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Honors Biology Lab Manual
Unit 3: Gene Expression, Mitosis & Differentiation
Unit 4: Meiosis, Genetics & Genetically Modified Organisms
Name: _______________________________________________
Teacher: _________________________
Period: ________
Honors Biology Lab Portfolio Rubric
Category
4
3
2
1
0
Lab 1*
All ​data,
calculations,
and pre/post
lab questions
are complete
and ​accurate.
1-2​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
3-4​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
5​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
> 5​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
Lab 2*
All ​data,
calculations,
and pre/post
lab questions
are complete
and ​accurate.
1-2​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
3-4​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
5​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
> 5​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
Lab 3*
All ​data,
calculations,
and pre/post
lab questions
are complete
and ​accurate.
1-2​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
3-4​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
5​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
> 5​ data,
calculations, or
pre/post lab
questions are
incomplete or
incorrect.
Labs are
connected back to
specific, restated
learning targets
Labs are listed or
stated with little
to no
explanation of
connections
Not included
Reflection
A
Labs are
thoroughly
connected back to
specific, restated
learning targets
Learning from labs
is explained with
some general
content included
Learning from
labs is sated with
little to no
content included
Not included
Reflection
B
Learning from labs
is ​thoroughly
explained with
specific content
included
Labs are
compared and
contrasted using a
graphic organizer
(Venn, T-Chart…)
Labs are
compared and
contrasted
Not included
Reflection
C
Labs are
thoroughly
compared and
contrasted using a
graphic organizer
(Venn, T-Chart…)
Specific example
of issues with ​any
labs or content
stated and how
issues were
corrected/learned
from
Specific example
of issues with
any​ labs or
content stated,
but doesn’t
include what was
learned
Not included
Reflection
D
Specific example
of issues with ​any
labs or content
thoroughly
explained and
how issues were
corrected/learned
from
Any labs or whole
unit are
thoroughly
connected to the
real world with
specific examples.
Any labs or whole
unit are
connected to the
real world with
specific examples.
Any labs or
whole unit are
stated to the real
world with some
examples.
Not included
Reflection
E
Score
Wei
ght
Total
Points
3.75
/15
3.75
/15
3.75
/15
1.0
/3
1.0
/3
1.0
/3
1.0
/3
1.0
/3
1
Article ^
Personal
Choice
Lab
Completion
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labs)
Grammar &
Spelling
Article
chosen
relates to
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summarized,
a ​copy is
included​ in
the portfolio,
and ​3​ or
more strong
connections
to the unit
are made.
Article chosen
relates to the
unit, is
summarized, a
copy is included​ in
the portfolio, ​2
strong
connections to the
unit are made
Article chosen
relates to the unit,
is summarized, a
copy is included​ in
the portfolio, ​1
strong connection
to the unit is made
Article chosen
relates to the
unit, is
summarized, and
a ​copy is
included​ in the
portfolio. ​No
connection or
very weak
connections to
the unit are
made
No article is
included,
summarized,
and connected
back to unit.
Item is
original​ and
complete
with a
rationale
that connects
3 or more
concepts ​to
the unit​. A
thorough​ and
accurate
explanation
of the
concepts is
included.
Item is ​original
and complete with
a rationale that
connects ​2
concepts ​to the
unit. ​An accurate
explanation of the
concepts is
included.
Item is ​original
and complete with
a rationale that
connects ​1
concept. An
accurate
explanation of the
concept is
included.
Item is ​original
and sloppy or
incomplete. No
rationale of the
concepts is
included or
item/explanation
of concepts is
inaccurate.
No personal
choice included
or item is not
original (copied
from Google,
labs, handouts,
etc).
All​ labs from
the unit are
complete.
1​ lab from the unit
is incomplete.
2​ labs from the
unit are
incomplete.
3​ labs from the
unit are
incomplete.
More than ​4
labs from the
unit are
incomplete.
1​ or fewer
errors in
complete
sentences,
spelling,
grammar, &
punctuation.
2​ errors in
complete
sentences,
spelling, grammar,
& punctuation.
3​ errors in
complete
sentences,
spelling, grammar,
& punctuation.
4 ​errors in
complete
sentences,
spelling,
grammar, &
punctuation.
5 ​or more
errors in
complete
sentences,
spelling,
grammar, &
punctuation.
3.75
/15
3.75
/15
1.5
/6
1.0
/4
Total Score
/100
* If you do not mark (*) the 3 labs you wish to be graded, the first 3 labs in your binder will be graded!*
^If you do not include a copy of your article, your score will be dropped by 1 point in the rubric (ex: you meet the
criteria for a “3” but have no copy of the article so you will earn a “2”)^
2
Units 3 & 4 Learning Targets
Unit 3:
1. Construct an explanation based on evidence for how the structure of DNA determines the structure of
proteins which carry out the essential functions of life through systems of specialized cells.
2. Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions
for characteristic traits passed from parents to offspring.
3. Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and
maintaining complex multicellular organisms.
Unit 4:
4. Make and defend a claim based on evidence that inheritable genetic variations may result from: (1) new
genetic combinations through meiosis, (2) viable errors occurring during replication, and/or (3)
mutations caused by environmental factors.
5. Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in
a population.
6. Analyze a major global challenge to specify qualitative and quantitative criteria and constraints for
solutions that account for societal needs and wants. (bioengineering/GMO)
7. Design a solution to a complex real-world problem by breaking it down into smaller, more manageable
problems that can be solved through engineering. (bioengineering/GMO)
3
Unit 3: Gene
Expression,
Mitosis &
Differentiation
4
Constructing DNA & RNA Models
Introduction:
Within the ​nucleus​ of every cell are long strings of DNA, the code that holds all the information needed to
make and control every cell within a living organism. DNA, which stands for ​deoxyribonucleic acid,
resembles a long, spiraling ladder. It consists of just a few kinds of atoms: carbon, hydrogen, oxygen, nitrogen,
and phosphorus. Combinations of these atoms form the ​sugar-phosphate backbone of the DNA​ -- the sides
of the ladder, in other words.Other combinations of the atoms form the four bases: ​thymine​ (T), ​adenine​ (A),
cytosine​ (C), and ​guanine​ (G). These bases are the rungs of the DNA ladder. (It takes two bases to form a
rung -- one for each side of the ladder.) A sugar molecule, a base, and a phosphate molecule group together to
make up a ​nucleotide​. Nucleotides are abundant in the cell's nucleus. Nucleotides are the units which, when
linked sugar to phosphate, make up ​one side of a DNA ladder​.
DNA is called the blueprint of life. It got this name because it contains the instructions for making every protein
in your body . Why are proteins important? Because they are what your muscles and tissues are made of;
they synthesize the pigments that color your skin, hair, and eyes; they digest your food they make (and
sometime are) the hormones that regulate your growth; they defend you from infection. In short, proteins
proteins determine your body’s form and carry out its functions. ​DNA determines what all of these proteins
will be.
How does a cell “read” the chemical message coded in its DNA in the form of specific base sequences? Part of
the answer lies with a second molecule in the nucleus of cells called ribonucleic acid (RNA). RNA is similar to
DNA in that its molecules are also formed from nucleotides. However, deoxyribose and thymine are not found
in RNA. Two other molecules,​ ribose​ and ​uracil ​(U), are present. Ribose replaces deoxyribose, and uracil
replaces thymine. Looking at their models, you will see certain similarities between the molecules that they
replace. RNA is important in assisting in the production of proteins because it, unlike DNA, can leave the
nucleus and carry instructions for protein production to the rest of the cell.
Activity:
The goal of this lesson is to:
● Construct a paper model of a DNA helix by making the fundamental unit of DNA (nucleotide)
● Construct a paper model of a RNA helix by making the fundamental unit of RNA (nucleotide)
● Each member of the class will make a small segment of a DNA double helix and then join them
to form a large ladder-like helix.
● Each member of the class will make a small segment of a RNA molecule and then join them to
form a large RNA molecule.
DNA Modeling Procedure:
1. Cut out the DNA model segments of deoxyribose, phosphate groups, and the bases provided. Color
them according to the following color-code:
● Deoxyribose: purple
● Phosphate: brown
● Adenine: blue
● Guanine: green
● Thymine: red
● Cytosine: yellow
2. Using the small circles and stars as guides, line up the bases, phosphates and sugars.
3. Now glue the appropriate parts together forming 4 total nucleotides.
5
4. Select 2 nucleotides to be the left half of your DNA molecule. Using the small squares as a guide, line
the 2 nucleotides up.
5. Glue the 2 nucleotides together, forming the left half of your DNA ladder.
6. Complete the right side of the ladder by adding the complementary bases. You will have to turn them
upside down in order to make them fit.
7. Glue the right side of the ladder together at the small squares and in the center where the bases meet.
Your finished model should look like a ladder.
8. Write your name on the back of your piece of DNA. Bring your pieces to the lab area and join them to
the class’ pieces to form a longer piece of DNA.
RNA Modeling Procedure:
1. Cut out the DNA model segments of deoxyribose, phosphate groups, and the bases provided. Color
them according to the following color-code:
● Ribose: pink
● Phosphate: brown
● Adenine: blue
● Guanine: green
● Uracil: orange
● Cytosine: yellow
2. Using the small circles and stars as guides, line up the bases, phosphates and sugars.
3. Now glue the appropriate parts together forming 4 total nucleotides.
4. Using the small squares as a guide, line the 4 nucleotides up.
5. Glue the 4 nucleotides together, forming a small segment of a RNA molecule.
6. Write your name on the back of your piece of RNA. Bring your pieces to the lab area and join them to
the class’ pieces to form a longer piece of RNA.
Questions
1. Five different nucleotides make up nucleic acids. What are they? What elements make up all
nucleotides?
2. The DNA molecule resembles a twisted ladder. Which 2 molecules of a nucleotide form the sides of a
DNA ladder? Which molecule of a nucleotide forms the rungs of a DNA ladder?
3. What bases pair together in DNA? What bases pair together in RNA?
4. If 30% of a DNA molecule is adenine, what percent is cytosine? SHOW YOUR WORK!
6
5. What 2 molecules are present in RNA nucleotides that are not found in DNA nucleotides?
6. Complete the table below comparing DNA and RNA (mark with a ✔ if the trait is present; leave the box
blank if it is absent).
DNA
RNA
Ribose present
Deoxyribose present
Phosphate present
Adenine present
Thymine present
Uracil present
Guanine present
Cytosine present
Double stranded
Single stranded
Remains in the nucleus
Moves out of the nucleus
7
DNA MODEL SEGMENTS:
8
9
RNA MODEL SEGMENTS:
10
11
DNA and Mutations Webquest
Answer all questions in complete sentences!
http://evolution.berkeley.edu/evolibrary/article/mutations_01
DNA and Mutations
1.​ ​What is a mutation?
2.​
​What
does DNA affect?
3.​
​Without
mutations, what would not occur?
DNA: The Molecular Basis of Mutations
1.​ ​What is DNA?
2.​
​What
3.​
​The
are the four basic units of DNA?
sequence of these bases encodes _____________________.
4.​ ​Some parts of DNA are __________________ that carry instructions for making ___________________ which are long chains of ________________________.
5.​
​What
are codons?
6.​ ​The cellular machinery uses these instructions to ____________________ a string of corresponding
amino acids.
7.​
​What
do “stop” codons signify?
Types of Mutations
1.​ ​What is a substitution?
2.​
​What
causes sickle cell anemia?
12
3.​
​What
are 3 things that a “substitution” mutation cause?
1.
2.
3.
4.​
​Copy
the example of a substitution mutation. (left side of page)
5.​
​What
is an insertion mutation?
6.​
​Copy
the example of an insertion mutation.
7.​
​What
is a deletion?
8.​
​Copy
the deletion example.
9.​
​What
is a frameshift mutation?
10.​ C
​ opy the example of the frameshift mutation.
Causes of Mutations
1.​ ​DNA fails to ______________ __________________.
2.​
​External
3.​
​What
_____________________ can create _________________________.
are two examples of external influences?
13
The Effects of Mutations
1.​ ​Where may mutations occur?
2.​
​What
are somatic mutations?
3.​
​What
are the only types of mutations that matter to large-scale evolution?
4.​
​What
are the effects of germline mutations?
1.
2.
3
5.​ ​While many mutations do indeed have negative effects, mutations can have major and
___________________ effects.
6.​
​What
are ​Hox genes?
7.​
​What
is the effect of a mutation in the H
​ ox gene?
8.​
​Weird
Fact: ​What happened to the fly with a ​Hox mutation?
A Case of the Effects of Mutation: Sickle cell mutation
1.​ ​What is sickle-cell anemia?
2.​
​People
with _________ copies of the gene have the disease.
3.​
​What
are the negative effects of the sickle cell gene?
4.​
​What
are some of the positive effects of sickle cell?
14
​ utations are Random
M
1.​ ​Mutations can be _________________, neutral, or _________________ to the organism.
2.​
​What
are two possible explanations for “resistant” lice?
3.​
​What
is directed mutation?
4.​
​In
5.​
​What
was their hypothesis?
6.​
​What
is the experimental set-up for the experiment?
1952, Esther and Joshua Lederberg performed and experiment that helped show . . .
1.
2.
3.
4.
5.
7.​ ​So, the penicillin-resistant bacteria were there in the ________________________ before they
encountered _________________________. They did not _________________________ resistance in
response to the exposure to the _____________________________.
15
Virtual Gene Expression Modeling
Go to the following site: ​http://www.zerobio.com/drag_oa/protein/overview.htm​ and read the overview and tips
for the activity. Click the next arrow at the bottom right of the page to begin the activity.
Transcription
Read the introduction to transcription. Drop and drag the bases and labels to simulate the process of
transcription. Once you have it correct (use the check answer button to determine this), fill in the
corresponding figure below.
Questions:
1. Which base in RNA is replaced by uracil?
2. How many mRNA codons are illustrated above?
3. What is the name of the enzyme that creates the mRNA copy from DNA?
4. What is the name of the sugar in the mRNA nucleotides?
5. What is the mRNA transcript for the DNA sequence TTACGC?
Click the next arrow to move on.
16
Translation
Read the introduction to translation. Drop and drag the bases and labels to simulate the process of translation.
Once you have it correct (use the check answer button to determine this), fill in the corresponding figure below.
Questions:
1. What organelle assists tRNA in translating the mRNA in the cytoplasm?
2. The role of tRNA is to carry a(n) _______________________________.
3. Is a tRNA anticodon more similar to DNA or RNA in nucleotide sequence?
4. If the mRNA codon was CGA, the tRNA anticodon that it binds with is ____________.
Click the next arrow to move on.
17
Protein Synthesis 1
Read the introduction to protein synthesis 1. Drop and drag the bases and labels to simulate the process of
protein synthesis. Once you have it correct (use the check answer button to determine this), fill in the
corresponding figure below.
Questions:
1. How many amino acids are coded for by the DNA?
2. What protein does this DNA code for?
3. If instead of ACT, the first DNA triplet was ACG, which amino acid would be coded for?
4. What amino acid is carried by a tRNA with the anticodon GUA?
Click the next arrow to move on.
18
Protein Synthesis 2
Drop and drag the bases and labels to simulate the process of protein synthesis. Once you have it correct
(use the check answer button to determine this), fill in the corresponding figure below.
Questions:
1. Other than UUU, what is another mRNA codon that codes for phenylalanine (PHE)?
2. What is the tRNA anticodon that binds to the codon you answered above?
3. The role of the ribosome is to help mRNA and tRNA interact. It is made of two subunits and is roughly
half __________ and half protein.
4. Sickle cell anemia is a disease of red blood cells in which a genetic mutation in DNA leads to a
mutation in hemoglobin. A single base change alters the DNA sequence C​T​C to C​A​C which codes for
the wrong amino acid. What amino acid is coded for by the n
​ ormal DNA sequence, CTC?
5. For the question above, what amino acid is coded for by the ​mutated DNA sequence, CAC?
19
Click the next arrow to move on.
Quiz
Take the quiz and record the ​correct​ answers for the questions below.
1. Transcription is the first step of protein synthesis and it occurs in the _______________________.
2. Translation is the second step of protein synthesis and it occurs in the ______________________.
3. If a DNA sequence consists of 12 nucleotides, how many RNA codons will there be? __________
4. The enzyme that creates mRNA from a DNA sequence is called __________________.
5. Each codon of the mRNA (hence each triplet in DNA) codes for one __________________________.
6. The specific amino acid carried by a tRNA is determined by its ____________________________.
7. When amino acids are brought in by tRNA, they are joined together by hydrolysis reactions to form the
growing protein.
True
False
8. Whenever a cell needs to, it can unzip DNA and make a transcript of a sequence so that a protein can
be made. DNA then zips up.
True
False
9. The same amino acid can be carried by different tRNAs.
True
False
10. Although not discussed in this activity translation actually takes place in 3 steps: ________________,
_______________, __________________.
20
How Are Proteins Made Anyway?
(Simulating Protein Synthesis)
Introduction
A ​gene​ is a series of bases on a DNA molecule that ​codes for a particular trait​, such as attached or unattached
earlobes, eye color, or blood type. You inherit genes from your parents. The order of the nucleotide bases in DNA
determines the ​sequence of amino acids​ in polypeptide chains, and thus the structure of proteins.
In a process called ​transcription​, which takes place in the nucleus of the cell, messenger RNA (mRNA) reads and
copies the DNA's nucleotide sequences in the form of a complementary
RNA molecule. Then the mRNA carries this information in the form of a code to the ribosomes, where protein
synthesis takes place. The code, in DNA or mRNA, specifies the order in which the amino acids are joined together to
form a polypeptide chain. The code words in mRNA, however, are not directly recognized by the corresponding
amino acids. Another type of RNA called transfer RNA (tRNA) is needed to bring the mRNA and amino acids together.
As the code carried by mRNA is "read" on a ribosome, the proper tRNAs arrive in turn and give up the amino acids
they carry to the growing polypeptide chain. The process by which the information from DNA is transferred into the
language of proteins is known as ​translation​.
In this activity, you will simulate the mechanism of protein synthesis and thereby determine the traits inherited by
fictitious organisms called ZWEEBLES. A ZWEEBLE, whose cells contain only one chromosome, is a member of the
kingdom Animalia. A ZWEEBLE chromosome is made up of six genes (A, B, C, D, E and F), each of which is responsible
for a certain trait.
Problem
1. How can the traits on a particular chromosome be determined?
2. How can these traits determine the characteristics of an organism?
Materials
Colored Pencils
Procedure
1. To determine the trait for Gene A of your ZWEEBLE, fill in the information in the box labeled GENE A in the
Data Table. Notice the sequence of nucleotides in DNA. On the line provided, write the sequence of
nucleotides of mRNA that are complementary to DNA. Then, on the line provided, write the sequence of
nucleotides of tRNA that are complementary to mRNA.
2. In order to determine the sequence of amino acids, match each ​mRNA​ triplet with the specific amino acid in
the codon tables (Figure 1a or 1b). Using a - (hyphen) to separate each amino acid number, record this
information in the appropriate place in the Data Table.
3. Using Figure 2, find the trait that matches the amino acid sequence. Record this information in the
appropriate place in the Data Table.
4. Repeat steps 1 through 3 for the remaining genes (B through F).
5. Repeat for all four zweebles (A-D).
6. Complete the analysis questions.
21
​FIGURE 1a
FIGURE 1b
22
FIGURE 2
ZWEEBLE-A
Gene A
DNA​
TGG
CCA
Gene B
ATA
DNA​
TCG
CTT
Gene C
DNA​
AAA
TTG
mRNA ___________________
mRNA ___________________
mRNA ________________
tRNA
tRNA
tRNA
___________________
___________________
________________
Amino Acid
Sequence __________________
Amino Acid
Sequence __________________
Amino Acid
Sequence _______________
Trait
__________________
Gene D
Trait
Trait
_______________
Gene F
DNA​
ACA
DNA​
DNA​
TAG TAG GAT
GCG
GCT
__________________
Gene E
CCC TCC TTT GGG
mRNA ___________________
mRNA ___________________
mRNA ________________
tRNA
tRNA
tRNA
___________________
___________________
________________
Amino Acid
Sequence __________________
Amino Acid
Sequence __________________
Amino Acid
Sequence _______________
Trait
Trait
Trait
__________________
__________________
________________
23
ZWEEBLE-B
Gene A
DNA​
TGG
AAA
Gene B
ATA
DNA​
AGT
TTA
Gene C
DNA​
AAA
TTT
mRNA ___________________
mRNA ___________________
mRNA ________________
tRNA
tRNA
tRNA
___________________
___________________
________________
Amino Acid
Sequence __________________
Amino Acid
Sequence __________________
Amino Acid
Sequence _______________
Trait
Trait
Trait
__________________
Gene D
DNA​
ACG
GCC
__________________
Gene E
CTT
DNA​
GAA TCC TTT GGA
_______________
Gene F
DNA​
TAT TAT CAC
mRNA ___________________
mRNA ___________________
mRNA ________________
tRNA
tRNA
tRNA
___________________
___________________
________________
Amino Acid
Sequence __________________
Amino Acid
Sequence __________________
Amino Acid
Sequence _______________
Trait
Trait
Trait
__________________
__________________
________________
24
ZWEEBLE-C
Gene A
DNA​
TGT
AGT
Gene B
AGC
DNA​
AGA
GCG
Gene C
DNA​
AAA
TTT
mRNA ___________________
mRNA ___________________
mRNA ________________
tRNA
tRNA
tRNA
___________________
___________________
________________
Amino Acid
Sequence __________________
Amino Acid
Sequence __________________
Amino Acid
Sequence _______________
Trait
Trait
Trait
__________________
Gene D
DNA​
ACA GCT
__________________
Gene E
TTA
DNA​
CAA GCC TTT GGG
_______________
Gene F
DNA​
TAT TAG CAA
mRNA ___________________
mRNA ___________________
mRNA ________________
tRNA
tRNA
tRNA
___________________
___________________
________________
Amino Acid
Sequence __________________
Amino Acid
Sequence __________________
Amino Acid
Sequence _______________
Trait
Trait
Trait
__________________
__________________
________________
25
ZWEEBLE-D
Gene A
DNA​
TGG
CCA
Gene B
ATA
DNA​
TCG
GCT
Gene C
DNA​
AAA
TTG
mRNA ___________________
mRNA ___________________
mRNA ________________
tRNA
tRNA
tRNA
___________________
___________________
________________
Amino Acid
Sequence __________________
Amino Acid
Sequence __________________
Amino Acid
Sequence _______________
Trait
Trait
Trait
__________________
Gene D
DNA​
ACG
GCG
__________________
Gene E
GCT
DNA​
CCC TCC TTT GGG
_______________
Gene F
DNA​
TAG TAG GAT
mRNA ___________________
mRNA ___________________
mRNA ________________
tRNA
tRNA
tRNA
___________________
___________________
________________
Amino Acid
Sequence __________________
Amino Acid
Sequence __________________
Amino Acid
Sequence _______________
Trait
Trait
Trait
__________________
__________________
________________
Analysis Questions
1. How are transcription and translation different?
2. Where does transcription take place in the cell? _________________________________
3. Where does translation take place in the cell? ___________________________________
4. How many tRNA nucleotides form an anticodon that will attach to the mRNA codon? _______
5. Suppose you knew the make-up of a specific protein in a cell. How could you determine the particular DNA
code that coded for that protein?
26
6. Create two additional traits for your ZWEEBLE . Create a new amino acid sequence, unlike any other
sequence in Figure 2. From the amino acid sequence you should be able to determine the tRNA anticodon,
mRNA codon, and the initial DNA sequence.
Trait #1 (you create this)
__________________
Trait #2 (you create this)
__________________
Amino Acid Sequence
_____________________
(Create a code by choosing sets of numbers from
Figure 1a or 1b.)
Amino Acid Sequence
_____________________
(Create a code by choosing sets of numbers from
Figure 1a or 1b.)
tRNA anticodon ___________________________
tRNA anticodon ___________________________
mRNA codon
___________________________
mRNA codon
___________________________
DNA code
___________________________
DNA code
___________________________
7. Using all the inherited traits, sketch your ZWEEBLE family portrait in the space below. Don't forget to use
colored pencils.
27
Mitosis – How Each New Cell Gets a Complete Set of Genes
Genes and Chromosomes
You probably already know that genes can influence a person's characteristics. For example, some people
have genes that result in sickle cell anemia or albinism (very pale skin and hair). In this section you will learn
how genes in chromosomes influence our characteristics.
Each cell in your body contains chromosomes. Each
chromosome ​contains a long molecule of DNA. Each
DNA molecule contains many genes. A ​gene i​ s a
segment of a DNA molecule that gives the instructions for
making a protein.
Different versions of the same gene are called
alleles​. Different alleles give the instructions for
making different versions of a protein. This
table shows the alleles for two human genes.
Allele
A
a
1.​ In the table, circle each symbol that
represents part of a DNA molecule. Underline
each word that is the name of a protein.
S
s
→ Protein
Normal enzyme for producing
→ melanin, a pigment molecule that
gives color to our skin and hair
Defective enzyme that cannot
→
make melanin
→ Normal hemoglobin
→ Sickle cell hemoglobin
Chromosomes come in pairs of ​homologous chromosomes​. In each pair of
homologous chromosomes, both chromosomes have the same genes at the
same locations. A gene may have different alleles on the two homologous
chromosomes (e.g. ​Aa​) or a gene may have the same alleles (e.g. ​SS​).
The table below shows how different ​genotypes​ (i.e. different combinations of
alleles) result in the production of different proteins which in turn result in
different ​phenotypes​ (i.e. different observable characteristics).
Genotyp
e
→
AA ​or ​Aa
→
aa
SS ​or​ Ss
ss
Protein
Enough normal enzyme to
make melanin in skin and hair
Defective enzyme for melanin
→
production
Enough normal hemoglobin to
prevent sickle cell anemia
Sickle cell hemoglobin, which
→ can cause red blood cells to
become sickle shaped
→
→
Phenotype​ (characteristics)
→
Normal skin and hair color
→
Very pale skin and hair color; albino
→
Normal blood; no sickle cell anemia
→
Sickle shaped red blood cells can block
blood flow in the smallest blood vessels,
causing pain, etc.; sickle cell anemia
2.​ Suppose that Jim has the alleles in the pair of homologous chromosomes shown in the above circle.
Is Jim's genotype ___​aaSs​
___​AaSs​
___​AaSS​?
Is Jim an albino? ___yes
___ no
Does Jim have ___ sickle cell anemia ___ normal blood?
28
3.​ Explain why a person with the ​aa​ genotype has very pale skin and hair color. Include the words enzyme and
melanin in your explanation.
4.​ Fill in the blanks of the following sentences.
A chromosome contains one long ______ molecule. Each gene in this ______ molecule gives the
instructions for making a ____________________.
Both chromosomes in a pair of ______________________ chromosomes have the same genes, but
the genes in these two _____________________ chromosomes may have different ____________.
Many of the genes on each chromosome give the instructions for making the large number of proteins that are
needed for normal cell structure and function. Therefore, ​each cell needs to have a complete set of
chromosomes with all of these genes​.
Cell Division – How New Cells Are Made
Each of us began as a single cell, so one important question is:
How did that single cell develop into a body with more than a trillion cells?
The production of such a large number of body cells is accomplished by ​cell division ​repeated many many
times. First, one cell divides to form two cells; then both of these cells divide to produce a total of four cells;
then these four cells divide to produce eight cells, etc. Thus, repeated cell division is needed for growth.
5.​ Even in an adult, some cells continue to divide. Why is cell division useful even in an adult who is no longer
growing? (Hint: Think about what happens when you have an injury that scrapes off some of your skin.)
Almost all the cells in our bodies are produced by a type of cell division called mitosis. In ​mitosis​, one cell
divides to produce two daughter cells, each with a complete set of chromosomes. (It may seem odd, but the
cells produced by cell division are called daughter cells, even in boys and men.)
6. ​Before mitosis begins, a cell makes a copy of all the DNA in each chromosome. What would go wrong if a
cell did not make a second copy of all of its DNA before the cell divided into two daughter cells?
29
Mitosis – How Each Daughter Cell Gets a Complete Set of Chromosomes
This figure shows mitosis for a cell that has a single pair of homologous chromosomes. To indicate that these
two homologous chromosomes have different alleles for many of their genes, one chromosome is shown as
dark or striped.
Preparation for Mitosis
To prepare for mitosis, the cell makes a copy of
the long DNA molecule in each chromosome; this
is called D
​ NA​ ​replication​. DNA replication
results in two identical copies of the DNA with the
same alleles for each of the genes.
Beginning of Mitosis
Each copy of the long DNA molecule is w
​ ound
tightly into a compact chromatid​. The two
chromatids in each chromosome are called
sister chromatids​; they are attached at a
centromere.
The chromosomes are ​lined up​ in the center of
the cell.
Mitosis continues
Next, the two sister chromatids of each
chromosome are separated. ​After they separate,
each chromatid is an independent chromosome.
Cytokinesis
The cell pinches together in the middle and
separates into two daughter cells​, each with a
complete set of chromosomes. Thus, each
daughter cell has a complete copy of all the
genes in the original cell.
The DNA in each chromosome u
​ nwinds​ into a
long thin thread.
7.​ Explain why the chromosomes in the second drawing have sister chromatids, but the chromosomes in the
third drawing do not. What happened to the sister chromatids?
30
8.​ This fill-in-the-blank question reviews the information from the previous page and provides some additional
information about six steps that are needed for mitosis to occur.
A. In preparation for mitosis, DNA is copied; this is called DNA ______________________.
B. Each copy of the DNA is wound tightly (condensed). Now each chromosome has two compact
sister ___________________. These compact chromosomes are easier to move than the long thin
chromosomes in a cell which is not undergoing cell division. S
​ pindle fibers ​which will move the chromosomes
begin to form.
C. Spindle fibers attach to the chromosomes and line up the chromosomes in the middle of the cell.
D. Spindle fibers pull the sister ___________________ apart to form separate chromosomes which are moved
toward opposite ends of the cell.
E. In a process called __________________________, the cell pinches in half, with one complete set of
chromosomes in each half.
F. Two identical _________________ cells are formed. Each _________________ cell has received a
complete set of chromosomes. The DNA in each chromosome unwinds into a long thin thread so that genes
can become active and give the instructions for making proteins.
9.​ For each of the figures below, give the letter of the corresponding step described above. Draw arrows to
indicate the sequence of events during cell division. (The figures show mitosis for a cell that has only 4
chromosomes (2 pairs of homologous chromosomes). The basic process is the same in a human cell which
has 46 chromosomes.)
10.​ Circle each pair of homologous chromosomes in step C. Use an * to mark the arrow you drew which shows
when sister chromatids separate to form individual chromosomes.
31
Modeling Mitosis with One Pair of Homologous Chromosomes
➢ Find a pair of model homologous chromosomes, one with the a
​ ​and​ s​ alleles
and the other with the ​A​ and ​S​ alleles. Both model chromosomes should be the
same color, but one model chromosome will have a stripe on both chromatids to
indicate that, although these two homologous​ ​chromosomes have the same
genes, they have different alleles for many of their genes. The shape of the
model chromosomes indicates that the DNA has already been copied and
wound tightly into sister chromatids.
➢ Sit across from your partner and u
​ se your arms to represent the spindle fibers​ that move the
chromosomes. Begin mitosis by lining up the model chromosomes in the middle of the cell (see figure
below). Use string to indicate the cell membrane that surrounds the cell that contains these
chromosomes.
➢ Demonstrate how the ​sister chromatids​ of each chromosome are ​separated​ into two separate
chromosomes which go to opposite ends of the cell.
➢ Now the cell is ready for ​cytokinesis w
​ hich will produce two daughter cells, each with a complete set of
chromosomes. Rearrange the string to demonstrate cytokinesis and then cut the string to form the cell
membranes surrounding each daughter cell.
➢ Model mitosis again and answer question 11. (To do this, you will first need to put the sister chromatids
of your model chromosomes back together. This does n
​ ot correspond to any biological process – it is
just necessary in order to continue your modeling activity.)
11.​ Record the results of your modeling in this figure. Draw and label the chromosomes in the oval and in the
daughter cells.
12.​ The original cell had the genetic makeup ​AaSs​. What is the genetic makeup of the daughter cells?
Are there any differences in genetic makeup between the original cell and the daughter cells produced by
mitosis?
32
Multiple Pairs of Homologous Chromosomes
Each human cell has ​23 pairs of homologous chromosomes​. Each of these pairs of homologous chromosomes
has its own unique set of genes. For example, human chromosome 11 has the genes that can result in
albinism and sickle cell anemia (as well as more than 1000 additional genes). Human chromosome 12 has
different genes, including a gene that can result in ​alcohol sensitivity​. This table shows the effects of the ​L​ and
l​ alleles of this gene.
Genotyp
e
→
LL ​or​ Ll
→
ll
Protein
Defective enzyme that cannot dispose of harmful
molecules produced by the metabolism of alcohol
Normal enzyme that disposes of harmful
→
molecules produced by alcohol metabolism
→
→
→
Phenotype​ (characteristics)
Skin flush and discomfort after
drinking alcohol
No flush or discomfort after
drinking alcohol
Modeling Mitosis with Two Pairs of Homologous Chromosomes
➢ Find a second pair of model homologous chromosomes, one with the L
​ ​ allele and the other with the l​ ​ allele.
Model mitosis for a cell with two pairs of homologous chromosomes.
13.​ Record the results of your modeling in this figure.
14.​ The original cell had the genetic makeup ​AaSsLl​. What is the genetic makeup of the daughter cells?
Are there any differences in genetic makeup between the original cell and the daughter cells produced by
mitosis?
33
Follow-Up Questions
15.​ Suppose that your partner has put the model chromosomes back together as shown in the diagram. What
is wrong? Explain why, in a real cell, sister chromatids could not have different alleles.
What is ​wrong​ with these
model chromosomes?
16.​ Each of the cells in your skin, brain, and other parts of your body has a complete set of chromosomes with
the same genes and the same alleles that were present in the single cell that developed into your body.
Explain how these billions of genetically identical cells were produced. Include the following terms in your
explanation: chromosome, cytokinesis, daughter cell, DNA replication, genes, mitosis, sister chromatids, and
spindle fibers.
Some animals and plants use a
combination of mitosis and splitting
off to reproduce. For example, a
hydra can reproduce by budding. The
bud is formed by many many
repetitions of mitosis, and then the
bud breaks off to form a daughter
hydra. (A hydra is an animal that
lives in the water and uses its
tentacles to catch food.)
17. ​Will there be any genetic differences between the mother hydra and the daughter hydra? Explain your
reasoning.
34
Stem Cells Webquest
In Google, type “Learn.Genetics” and click on the first link. Scroll down to the bottom and click on the “Stem
Cells” link.
1​st​ – Click on “The Nature of Stem Cells”
1. What are ​differentiated cells?
2. Are stem cells “differentiated” cells? Explain!
3. Circle: ​True or ​False, for the first few divisions, cells remain undifferentiated. If false, explain why below.
4. What is the embryo called after one week of fertilization?
5. What is the name given to the part of the embryo will eventually form all the cells of the body?
6. Cell signals ________________ the potential of the embryo cells about two weeks after fertilization. Each
layer will give rise to a __________________ set of cell types.
7. Circle: ​True or ​False, after birth, some stem cells remain. If false, explain why below.
8. What are the possible functions of stem cells in the body?
9.Circle: ​True or ​False, (adult) somatic stem cells are the same as embryonic stem cells. If false, explain why
below.
10. List other tissues where (adult) somatic cells have been found.
35
2​nd​- Go back to the “Stem Cells” home page and click on “Go Go Stem Cells.”
11. What is a stem cell niche?
12. What happens to a stem cell if it is removed from its niche?
13. Explore ​three of the five​ cell niches shown on the right side of the screen. Write three interesting facts
about the cell niches that you have chosen to explore.
Interesting Facts:
Cell Niche
Type:________________
_
Cell Niche
Type:________________
Cell Niche
Type:_________________
1.
1.
1.
2.
2.
2.
3.
3.
3.
3​rd​- Go back to the “Stem Cells” home page and click on “Unlocking Stem Cell Potential.”
14. Define regeneration.
15.Circle: ​True or ​False, regeneration in humans is limited. If false, explain why below.
16. List three examples of regenerative medicine that scientists are currently using.
1.
2.
3.
17.How are stem cells similar to cancer?
36
Regeneration in Planarians Lab
Introduction
Before we begin this lab, you need to do some research about planarians and their regenerative properties.
Please research and answer the following questions.
About regeneration:
1. What is cell differentiation? How does this happen?
2. How is gene expression/protein synthesis related to cell differentiation?
3. What are stem cells? Why are they important?
4. What is regeneration? How is regeneration a useful process for organisms?
About planarians:
1. In what environment(s) are planarians normally found in nature?
2. What is the purpose of the planarian’s photoreceptors found in the eyespots?
3. H
​ ow do planarians reproduce? (there are two ways, explain both)
4. Describe how planarians regenerate when cut (use information from at least three different reliable
websites).
5. Identify two ways in which planarians are being used for research.
Watch the video: http://www.hhmi.org/biointeractive/planarian-regeneration-and-stem-cells
37
Purpose
● To test the planarian’s ability to regenerate.
● To determine where stem cells are located in the planaria, based on the length of time it takes for the
photoreceptors in the eye spots to reappear.
Hypothesis
Materials
·​ ​planarian culture (​Dugesia dorotocephala)
·​ ​disposable scalpels
·​ ​dropping pipets
·​ ​petri dishes
·​
·​
·​
·​
​permanent
marker
​stereomicroscope/dissecting
​spring
​paper
scope
water
towels
Procedure
1. Number the bottoms of three of the petri dishes 1 through 3, fill halfway with
spring water, and set aside. (Marking the bottoms will prevent confusion by
accidental swapping of lids.)
2. Using a plastic transfer pipette, transfer a planarian into the remaining
unlabeled empty plastic petri dish.
3. Soak up excess water with a paper towel. Limiting the amount of water can
reduce the mobility of the planarian and facilitate the next step. Be careful not
to touch the planarian—they will stick to the paper and could then die.
4. Place the petri dish with the planarian under the dissecting microscope
WITHOUT turning the light on. Focus.
5. Using a scalpel, make Cut #1 to the planarian as indicated on the diagram on
the right. ​Planarians can move rapidly. Cutting them in a precise location can
be difficult.
6. Using a transfer pipette, gently transfer the head fragment into the petri dish
#1.
7. Repeat steps 5-6 for Cut #2, placing the mid-section in petri dish #2 and tail section in petri dish #3.
8. Repeat steps 2 through 7 with the remaining worms until dishes have at least three or four tail
fragments of each of the three cutting positions.
9. On the data table, record the time and room temperature when finished cutting all the planarians.
10. Monitor planarians daily, recording d
​ etailed, specific observations of their regeneration.
38
Data Table
Title: __________________________________________________________________________________
Day
1
Time
Temp. (°C)
Segment #
Photoreceptors?
Observations (movement,
changes, etc.)
1
2
3
2
1
2
3
1
3
2
3
39
Day
4
Time
Temp. (°C)
Segment #
Photoreceptors?
Observations (movement,
changes, etc.)
1
2
3
5
1
2
3
Questions
1. After you cut your planarian, how did the mobility of the tail fragments differ from the mobility of the
head fragments? Do they move the same or differently? If they move differently, why do you think this
is?
2. Did you notice a difference in the mobility of the tail pieces as the head regenerated? Explain what you
saw and why this might be.
40
3. Describe the regeneration of piece 1 over time. Did it result in a complete (with eyespots and tail)
planarian?
4. Describe the regeneration of piece 2 over time. Did it result in a complete (with eyespots and tail)
planarian?
5. Describe the regeneration of piece 3 over time. Did it result in a complete (with eyespots and tail)
planarian?
6. Discuss how the color of the regenerating parts changed over time? Explain why this difference in
coloring may have occurred.
7. When the heads were growing back, do you think the eyespots were functional? How would you test
this?
8. Did all the fragments regenerate photoreceptors at the same rate? Which were slower and which were
faster? (give specific piece numbers and days)
9. What does the rate of appearance of photoreceptors in the different fragments tell you about the
regeneration ability of different sections of the worm? Based on your data, where might the main stem
cell niche be for the planarian? Why did you choose this area?
41
Conclusion
Write a formal conclusion for this lab as if it were a formal lab report. To demonstrate that you really
understand the data and what it means, you should make connections between the information you learned
about stem cells and the regeneration qualities of the planarian. (Use the terms stem cells, differentiation, and
mitosis in your conclusion and make the connections!)
42
43
Unit 4: Meiosis,
Genetics &
Genetically
Modified
Organisms
Meiosis and Fertilization – Understanding How Genes Are Inherited
Almost all the cells in your body were produced by mitosis. The only
exceptions are the ​gametes​ – sperm or eggs – which are produced by a
different type of cell division called ​meiosis​.
During ​fertilization ​the sperm and egg unite to form a single cell called the
zygote​ which contains all the chromosomes from both the sperm and the
egg. The zygote divides into two cells by mitosis, then these cells each
44
divide by mitosis, and mitosis is repeated many times to produce the cells in an embryo which develops into a baby.
1.​ Each cell in a normal human embryo has 23 pairs of homologous chromosomes, for a total of 46 chromosomes per
cell. How many chromosomes are in a normal human zygote? Explain your reasoning.
2.​ What would happen if human sperm and eggs were produced by mitosis? Explain why this would result in an
embryo which had double the normal number of chromosomes in each cell.
A human embryo with that many chromosomes in each cell would be abnormal and would die before it could develop
into a baby. So, gametes ​cannot be made by mitosis.
3.​ Each human sperm and egg should have __​__ chromosomes, so fertilization will produce a zygote with ____
chromosomes; this zygote will​ develop into a healthy embryo ​with ____ chromosomes in each cell.
4.​ ​Each sperm and each egg produced by meiosis has only one chromosome from each pair of homologous
chromosomes​. When a sperm and egg unite during fertilization, the resulting zygote has ____ pairs of homologous
chromosomes. For each pair of homologous chromosomes in a zygote, one chromosome came from the egg and the
other chromosome came from the _______________.
A cell that has pairs of homologous chromosomes is ​diploid​.
A cell that has only one chromosome from each pair of homologous chromosomes is ​haploid​.
5.​ Next to each type of cell in the above chart, write:
● ​the number of chromosomes in that type of cell
● a ​d​ for diploid cells or an ​h​ for haploid cells.
Meiosis – Cell Divisions to Produce Haploid Gametes
Before meiosis, the cell makes a copy of the DNA in each chromosome. Then, during meiosis there are ​two cell
divisions​, Meiosis I and Meiosis II. These two cell divisions ​produce four haploid daughter cells​.
Meiosis I​ is different from mitosis because each pair of homologous chromosome lines up next to each other and then
the two homologous chromosomes separate. (The figure shows Meiosis I for a cell with a single pair of homologous
chromosomes; the stripes on the chromatids of one of the chromosomes indicates that this chromosome has
different alleles than the other homologous chromosome.)
45
Meiosis I produces daughter cells with half as many chromosomes as the parent cell, so the daughter cells are
haploid. Each daughter cell has a different chromosome from the original pair of homologous chromosomes.
6. ​In the figure for Meiosis I, label the diploid cell, the pair of homologous chromosomes in this diploid cell, and the
two sister chromatids in one of these chromosomes.
7.​ Do the chromosomes in the two daughter cells produced by Meiosis I have the same alleles for each gene? Explain
your reasoning.
Meiosis II​ is like mitosis since the sister chromatids of each chromosome are separated. As a result, each daughter cell
gets one copy of one chromosome from the pair of homologous chromosomes that was in the original cell. These
haploid daughter cells are the gametes.
​8.​ Use asterisks to indicate the cells in this figure that represent sperm produced by meiosis.
Modeling Meiosis to Understand How Meiosis Produces Genetically Diverse Gametes
To model meiosis, you will use the same pairs of model homologous chromosomes that you used to model mitosis. A
person with these chromosomes would have the genotype ​AaSsLl​.
9.​ What phenotypic characteristics would a person with this genotype have? Circle the appropriate phenotypic
characteristics in this table.
46
You will begin modeling meiosis with only one pair of the model chromosomes.
➢ Use this pair of model chromosomes to ​model each step of meiosis.​ Use
string to model the cell membranes at each stage.
10. ​Show the results of your modeling in this figure. Sketch and label the chromosomes in each cell that is produced
by Meiosis I and by Meiosis II.
11.​ You have modeled meiosis, beginning with a diploid cell that has the alleles ​AaSs.​ The haploid gametes produced
by meiosis have the alleles: __ ​AS​ or ​as
__ ​AASS​ or ​aass
__ ​AaSs
Next, you will model meiosis using both pairs of model chromosomes. At the beginning of Meiosis I each pair of
homologous chromosomes lines up independently of how the other pairs of homologous chromosomes have lined
up. This is called ​independent assortment​. As a result of independent assortment, at the beginning of Meiosis I the ​as
chromosome can be lined up on the same side as either the ​l​ chromosome or the ​L​ chromosome (see figure).
➢ Use your four model chromosomes to model Meiosis I and Meiosis II for both of the possible ways of lining up
the model chromosomes at the beginning of Meiosis I.
47
12.​ Record the results of your modeling in this chart.
When a pair of homologous chromosomes is lined up next to each other during
Meiosis I, the two homologous chromosomes can exchange parts of a chromatid.
This is called ​crossing over.
13a.​ On each chromatid of the chromosomes in the bottom row of this figure,
label the alleles for the genes for albinism and sickle cell anemia.
When these chromosomes and chromatids separate during Meiosis I and II, this
produces gametes with four different combinations of alleles for the genes for
albinism and sickle cell anemia.
13b.​ The combinations of alleles in the different gametes are:
__​AS​__
_____
_____
_____
14a.​ Explain why different gametes produced by the same person can have
different combinations of alleles for genes that are located on two different
chromosomes.
48
14b.​ Explain why different gametes produced by the same person can have different combinations of alleles for two
genes that are located far apart on the same chromosome
Comparing Mitosis and Meiosis
15a.​ In this figure, label the column that shows meiosis and the
column that shows mitosis.
15b.​ What are some similarities between cell division by mitosis
and cell division by meiosis?
These diagrams show mitosis and meiosis
after DNA has been replicated and wound
tightly into sister chromatids. The dotted
lines represent cytokinesis.
​15c.​
Complete this table to describe some important differences between mitosis and meiosis.
Characteristic
Mitosis
Meiosis
# of daughter cells
Type of cells produced
Genetic differences or similarities between daughter
cells
# of cell divisions
16. ​Complete these diagrams to show how a pair of
homologous chromosomes is lined up in a cell at the
beginning of mitosis vs. the beginning of meiosis I.
49
17.​ Match each item in the top list with the appropriate match from the bottom list.
Mitosis separates _____
Meiosis I separates _____
Meiosis II separates _____
a. pairs of homologous chromosomes
b. sister chromatids
18.​ Explain why sexually reproducing organisms need to have two different types of cell division. What are the
advantages of mitosis and of meiosis?
Analyzing Meiosis and Fertilization to Understand Inheritance
In this section you will learn how events during meiosis and fertilization determine the genetic makeup of the zygote
which in turn determines the genotype of the baby that develops from the zygote.
You already know that sisters or brothers can have different characteristics, even though they have the same parents.
One major reason for these different characteristics is that the processes of meiosis and fertilization result in a
different combination of alleles in each child.
You will model meiosis and fertilization for a very simplified case where there is only one pair of homologous
chromosomes per cell and only one identified gene on each chromosome.
➢ To produce the two pairs of model chromosomes shown in this figure, you will need a pair of the ​as​ and ​AS
model chromosomes in one color and a pair of the ​l​ and ​L​ model chromosomes in a different color. Tape
blank strips of paper on these model chromosomes to cover the ​S​, ​s​, ​L​, and ​l​ alleles. Then, tape strips with the
a ​and ​A​ alleles to create a second pair of model chromosomes which have the ​a​ and ​A​ alleles.
Modeling Meiosis and Fertilization to Understand Inheritance
➢ One person in your group should use one pair of model homologous chromosomes to demonstrate how
meiosis​ produces sperm. Another person should use the other color pair of model homologous chromosomes
to demonstrate how meiosis produces eggs.
50
19.​ For each type of sperm and egg produced by meiosis, write the allele in an appropriate white box in this chart.
➢ Use chalk to outline the rectangles of this chart on your lab table. Put a model chromosome for each type of
sperm and egg in each of the boxes on the top and on the left.
➢ Use one of the sperm to ​fertilize​ one of the eggs to produce a zygote. The resulting zygote will have one
chromosome from the egg and one from the sperm. Note the genetic makeup of this zygote in the
appropriate gray box in the chart above.
➢ Model fertilization three more times, pairing each type of sperm with each type of egg.
20. ​Write the genetic makeup of each type of zygote in the appropriate box in the shaded area in the chart.
21.​ Each person began as a zygote. Explain why each person has the same genetic makeup as the zygote he or she
developed from.
22.​ In the above chart, write in the phenotypic characteristic (albinism or normal skin and hair color) for the mother,
the father, and the person who would develop from each zygote. Circle the zygotes that would develop into a person
with the same phenotypic characteristic as the parents. Use an * to mark the zygote that would develop into a person
who would have a different phenotypic characteristic that neither parent has.
23a​. Explain why many children have the same phenotypic characteristics as their parents.
23b.​ Explain how a child can have a different phenotypic characteristic that neither parent has.
Why are siblings different from each other?
Your analysis of the inheritance of a single gene showed how meiosis and fertilization can result in genetic and
phenotypic differences between siblings produced by the same mother and father. Now you will analyze the results
of meiosis and fertilization for multiple genes. You will see how meiosis and fertilization result in the many genetic
and phenotypic differences between siblings.
51
Remember that ​AaSsLl​ parents can produce multiple different types of gametes with different combinations of the
alleles for the albinism gene, sickle cell gene, and alcohol sensitivity gene (see page 4). As a result of independent
assortment and crossing over, an​ AaSsLl​ parent can produce eight types of gametes: ​asl, ASL, asL​, ​ASl, aSl, aSL​, ​AsL
and ​Asl​.
Obviously, fertilization of the eight different types of eggs by the eight different types of sperm could result in
offspring with many different genotypes. In question 24, you will describe the outcomes for fertilization of a few of
the possible types of eggs by one of the possible types of sperm.
24.​ Complete the following chart to describe the genetic makeup and phenotype of some of the possible outcomes of
fertilization between the different types of eggs and sperm produced by ​AaSsLl​ parents.
Alleles
in egg
Alleles
in sperm
Alleles in
zygote
ASL
asl
AaSsLl
ASl
asl
aSl
asl
Phenotype of person who will develop from this zygote
(Hint: See the table in question 9 on page 38.)
This illustrates how, even when we consider only three genes with two alleles each, meiosis and fertilization can
produce zygotes with many different combinations of alleles which can develop into people with many different
combinations of phenotypic characteristics. The actual amount of ​genetic diversity​ possible in the children produced
by one couple is much greater, since each person has thousands of genes on 23 pairs of homologous chromosomes.
25.​ Explain why no two siblings have exactly the same combination of alleles inherited from their parents (except for
identical twins who both developed from the same zygote). Begin with the observation that each person has
thousands of genes on 23 pairs of homologous chromosomes. Include in your explanation the terms genes, alleles,
chromosomes, meiosis, independent assortment, crossing over, eggs, sperm, fertilization, and zygote​.
A Mistake in Meiosis Can Cause Down Syndrome
You have seen that normal meiosis and fertilization can produce a lot of genetic variability in the different children
produced by the same parents. Additional genetic variability can result from mistakes in DNA replication (which can
cause mutations) or mistakes in meiosis. For example, when meiosis does not happen perfectly, the chromosomes are
52
not divided equally between the daughter cells produced by meiosis, so an egg or a sperm may receive two copies of
the same chromosome.
26.​ Suppose that a human egg receives two copies of a chromosome, and this egg is fertilized by a normal sperm.
How many copies of this chromosome would there be in the resulting zygote? ____
- How many copies of this chromosome would there be in each cell in the resulting embryo? ____
When a cell has three copies of a chromosome, the extra copies of the genes on this chromosome result in abnormal
cell function and abnormal embryonic development. To understand how an extra copy of one chromosome could
result in abnormalities, remember that each chromosome has genes with the instructions to make specific types of
proteins, so the extra chromosome could result in too many copies of these specific proteins. Think about what would
happen if you added too much milk to a box of macaroni and cheese. The mac and cheese would have too much
liquid and be runny instead of creamy. Cells are much more complicated than mac and cheese, and a cell cannot
function properly when there are too many copies of some types of proteins due to an extra copy of one of the
chromosomes.
When the cells in an embryo do not function properly, the embryo develops abnormalities. For example, some babies
are born with an extra copy of chromosome 21 in each cell. This results in ​Down syndrome ​with multiple
abnormalities, including mental retardation, a broad flat face, a big tongue, short height, and often heart defects.
This figure shows a karyotype for a normal boy. A ​karyotype​ is a photograph of a magnified
view of the chromosomes from a human cell, with pairs of homologous chromosomes
arranged next to each other and numbered. In the karyotype, each chromosome has double
copies of its DNA, contained in a pair of sister chromatids linked at a centromere.
27.​ Label the sister chromatids in chromosome 3 in the karyotype.
- Draw in an extra chromosome 21 to show the karyotype of a boy with Down syndrome.
28.​ In most cases, an embryo which has an extra chromosome in each cell develops such severe abnormalities that
the embryo dies, resulting in a miscarriage. For example, an extra copy of any of the chromosomes in the top row of
the karyotype results in such severe abnormalities that the embryo always dies. In contrast, an extra copy of
chromosome 21 results in less severe abnormalities so the embryo can often survive to be born as a baby with Down
syndrome. What do you think is the reason why a third copy of chromosome 1, 2, 3, 4 or 5 results in more severe
abnormalities than a third copy of chromosome 21?
Chromosomal Mutations & Karyotyping
Purpose: ​to explain what a chromosomal mutation is and how a human karyotype is used to identify
specific genetic disorders
Introduction
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Each species has a characteristic number of chromosomes; for example, corn cells have 20
chromosomes, mouse cells have 40 chromosomes, and human cells have 46 chromosomes. In order
to view the chromosomes so that they may be counted, a cell will be allowed to reproduce and
colchicine is added to stop the cell division during metaphase. The resulting cells are placed in a
hypotonic solution that causes the cell membranes to rupture. The chromosomes are stained and
photographed. The chromosomes may then be cut out of the photograph and arranged by
homologous pairs according to ​size, position of the​ ​centromere and the characteristic banding
pattern​. The resulting display is called a ​karyotype​. See ​Figure I.
Figure I: Karyotyping Procedure
Part I - The Normal Human Karyotype
The normal human karyotype is composed of 46 total chromosomes. The first 22 pairs
(chromosomes 1-22)​ ​are known as ​autosomes ​(code for general human traits); the 23​rd​ pair is known
as the sex chromosomes ​(X and Y). ​Females have two X chromosomes (XX) and males have one X
chromosome and one Y chromosome (XY).
1. ​Observe the normal human karyotype chart found in ​FIGURE II (next page)​.
Figure II – Normal Human Karyotype Chart
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Q1.​ What is the total number of chromosomes found in this cell? ______________________________
Q2. ​How many autosomal chromosomal ​pairs​ are visible in the above karyotype? ​________________
Q3.​ What are the THREE chromosome characteristics used to organize the karyotype?
Q4.​ What is the sex of the above individual? _____________
Q5.​ Could two individuals have the same karyotype? Explain.
Part II – Identifying Genetic Disorders
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Karyotypes can be used to identify a number of ​chromosomal mutations​. Chromosomal mutations can result
in changes in the number of chromosomes in a cell or changes in the structure of a chromosome. Unlike a
gene mutation which alters a single gene or larger segment of DNA on a chromosome, chromosome mutations
change and impact the entire chromosome. Nondisjunction is the failure of chromosomes to separate properly
during meiosis. This can result in monosomy (one chromosome instead of a pair) and trisomy (three
chromosomes instead of a pair) conditions, as well as chromosomes with missing or extra segments. See
Table I​ for some of the genetic conditions and clinical effects caused by chromosomal mutations.
Table I
Q6. ​What is the difference between monosomy and trisomy?
Q7.​ How could nondisjunction result in an individual with Down syndrome?
2. ​Observe the abnormal human karyotype chart found in ​FIGURE III​.
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FIGURE III​ ​– Abnormal Human Karyotype Chart
Q8.​ What is the sex of the individual? ​______________
Q9.​ What is the total chromosome count? __________ Is this normal? __________
Q10.​ Using Table I, identify the condition present in this individual. ​____________________
Part III – Internet Activity
The following site has an interactive karyotype activity. Go to the site and read the introduction, then click on
the patient histories.
http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping.html
Start with Patient A and complete the karyotype. Answer the questions below and repeat for Patients B and C.
Q11.​ What notation would you use to characterize Patient A’s karyotype? ______________
Q12.​ What diagnosis would you give Patient A? _____________
Q13.​ What notation would you use to characterize Patient B’s karyotype? ______________
Q14.​ What diagnosis would you give Patient B? _____________
Q15.​ What notation would you use to characterize Patient C’s karyotype? ______________
Q16.​ What diagnosis would you give Patient C? ______________
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Genetics
We all know that children tend to resemble their parents. Parents and their children tend to have similar appearance
because children inherit genes​ ​from their parents and these genes influence characteristics such as skin and hair
color.
How do genes influence our characteristics?
1. ​A ​gene​ is a segment of a ________ molecule that gives the instructions for making a protein. Different versions of
the same gene are called ​alleles​, and different alleles give the instructions for making different versions of a
__________________. The different versions of a protein can result in different observable characteristics (i.e.
different ​phenotypes​).
Each cell in your body has two copies of each gene (one inherited from your mother and one inherited from your
father).
·​ ​If both copies of a gene have the ​same​ allele, the person is ​homozygous​ for that gene.
·​ ​If the two copies of a gene have ​different​ alleles, the person is ​heterozygous​ for that gene.
This chart shows an example of how genes influence our characteristics.
2.​ Circle the genotypes in the chart that are homozygous. Explain how these two different homozygous genotypes
result in different phenotypes. What is the molecular mechanism?
3a. ​In a heterozygous person, often a ​dominant​ allele determines the phenotype and the other ​recessive​ allele does
not affect the phenotype. This means that a heterozygous person has the same phenotype as a person who is
homozygous for the ___________________ allele.
(dominant/recessive)
For example, a person who is heterozygous ​Aa​ has the same phenotype as a person who is homozygous ​AA​ because
skin cells that have at least one ​A​ allele produce enough melanin to result in normal skin color.
3b. ​For this gene, which allele is dominant? ___ ​A
___ ​a
- Which allele is recessive? ___ ​A ___ ​a
- What evidence supports your conclusion about which allele is dominant and which is recessive?
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How does a baby inherit genes from his or her mother and father?
Each gene is a part of a DNA molecule which is contained in a ​chromosome​.
During ​meiosis​, the gene-carrying chromosomes move from the parent’s cells to
the gametes, and during ​fertilization​, the gene-carrying chromosomes move
from the gametes to a zygote which develops into a baby. Thus, we can
understand how a baby inherits genes from his or her mother and father by
understanding how the gene-carrying chromosomes move during meiosis and
fertilization.
Inheritance of Albinism
To learn more about how genes are inherited, we will start with a specific question:
If both parents are heterozygous (​Aa​), what different combinations of ​A​ and/or ​a​ alleles could be observed in
the children of these parents?
To answer this question, your group will use model chromosomes to show how meiosis and fertilization result in
inheritance. Each parent will have a pair of homologous chromosomes, one with an ​A​ allele and the other with an ​a
allele.
➢ ​One of you should use your model chromosomes
to demonstrate how meiosis produces different
types of eggs, and another group member should
demonstrate how meiosis produces different
types of sperm.
4. ​In​ ​this chart, record the allele in each type of egg
produced by meiosis. Record the allele in each type of
sperm.
➢ ​Next, use chalk to outline the rectangles shown in
this chart on your lab table and put a model
chromosome for each type of sperm and egg in
the appropriate positions. Model fertilization for
each type of sperm and egg.
5. ​Record​ ​the genetic makeup (the alleles) for each type of zygote produced by
fertilization.
Biologists use a similar chart to analyze inheritance However, biologists omit much of the
detail shown above and use a simplified version called a ​Punnett Square​.
6. ​For this Punnett square:
-Write "gametes" and draw arrows to each symbol that represents the genetic makeup of
a gamete.
-Write "zygotes" and draw arrows to each symbol that represents the genetic makeup of a zygote.
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7.​ The genetic makeup of each zygote in the Punnett square represents a possible genotype of a child of this couple.
Explain why the genotype of each child is the same as the genetic makeup of the zygote that he or she developed
from.
8.​ For an ​Aa​ mother, what fraction of her eggs have an ​a​ allele? _____
- What fraction of an ​Aa​ father's sperm have an ​a​ allele? _____
- What fraction of this couple's children would you expect to have the ​aa​ genotype? _____
- Explain your reasoning.
10.​ For each of the ​four​ Punnett squares above (from #8 and #9), circle the genotype of anyone who would have
normal skin and hair color.
- In these four Punnett squares there is only one example of a child who would have a different phenotype that was
not observed in either parent. Use an * to indicate this example.
Notice that all of the children with normal skin and hair color have at least one parent who also has normal skin and
hair color. Also, almost all of the albino children have at least one albino parent. These findings fit with our general
observation that children tend to resemble their parents.
11.​ Explain why two albino parents will not have any children with normal skin and hair color, but two parents with
normal skin and hair color could have an albino child.
12.​ Albino children are rare in the general population. Based on this observation, what is the most common genotype
for parents? Explain your reasoning.
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Coin Toss Genetics
The way genes behave during meiosis and fertilization can be modeled by using two-sided coins, where heads
represent the dominant allele (​A​) and tails represent the recessive allele (​a​). This table explains how the coin toss
model of inheritance represents the biological processes of meiosis and fertilization for heterozygous (​Aa​) parents.
Biological Process
How This Will Be Modeled in Coin Toss Genetics
Meiosis​ in an ​Aa​ parent produces gametes. Each
gamete has an equal probability of having an ​A​ allele
or an ​a ​allele.
You toss your coin and check for heads up vs. tails
up. This represents the 50-50 chance of getting an
A​ allele or an ​a ​allele.
Fertilization​ of an egg by a sperm produces a zygote.
Each gamete contributes one allele to the genotype of
the child that develops from the zygote.
Two students each toss a coin and the result of
this pair of coin tosses indicates the genotype of
the child that develops from the zygote.
➢ Find someone to “mate” with.
➢ Each of you will toss your coin; record the results as the genotype of the first child in the first family of four
children in the table below. Make three more pairs of coin tosses and record the genotypes for the second,
third and fourth children in this family.
➢ Repeat this procedure three times to determine the genotypes for three more families of four children each,
and record your results in the table.
➢ Complete the last three columns for these four families of coin toss children, and add your results. Give your
teacher the total numbers for the ​AA​, ​Aa​ and ​aa​ genotypes.
➢ Use a checkmark (✔) to indicate any coin toss family of 4 children that has exactly the numbers of ​AA​, ​Aa​ and
aa​ genotypes predicted by the Punnett square.
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To understand why some of the coin toss families do not have exactly the predicted number of children with each
genotype, answer these questions.
1. ​Does the genotype produced by the first pair of coin tosses have any effect on the genotype produced by the
second pair of coin tosses? ___ yes ___ no
2.​ If a coin toss family has one ​aa​ child, could the second child in this family also have the ​aa​ genotype? ___ yes
___ no
Explain your reasoning.
In real families the genotype of each child depends on which specific sperm fertilized which specific egg, and this is
not influenced by what happened during the fertilizations that resulted in previous children. Therefore, the genotype
of each child is independent of the genotype of any previous children.
3.​ Suppose that a mother and father who are both heterozygous ​Aa​ have two children who also are heterozygous ​Aa​.
If this couple has a third child, what is the probability that this third child will also be heterozygous ​Aa​?
- Explain your reasoning.
As a result of random variation in which particular sperm fertilizes which particular egg to form a zygote, the
proportions of each genotype and phenotype vary in different families, and the observed proportions of each
genotype and phenotype often do not match the predictions of the Punnett square.
4.​ Suppose that you had data for 20 families of four children each where both parents were heterozygous ​Aa​. Would
each of these families have exactly one albino child, as predicted by the Punnett square? Explain why or why not.
5. ​Your teacher will give you the class data to enter in the last line of the table on page 51. Are the percents of each
genotype in the class data similar to the predictions of the Punnett Square?
The random variation observed in small samples usually averages out in large samples. Therefore, the predictions of
the Punnett Square are usually more accurate for larger samples of children.
Genetics of Sickle Cell Anemia
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Red blood cells are full of ​hemoglobin​, the protein that carries oxygen. One hemoglobin allele codes for normal
hemoglobin, and another allele codes for ​sickle cell hemoglobin​. In a person is ​homozygous for the sickle cell allele​,
sickle cell hemoglobin tends to clump into long rods that cause the red blood cells to assume a sickle shape or other
abnormal shapes, instead of the normal disk shape. This causes a disease called ​sickle cell anemia​.
1.​ Normal disk-shaped red blood cells can barely squeeze through the capillaries (the tiniest blood vessels). What
problems might be caused by red blood cells that are sickle-shaped or have other abnormal shapes?
2.​ Most children with sickle cell anemia have parents who do not have sickle cell anemia. Explain how a person can
inherit sickle cell alleles from parents who do not have sickle cell anemia. Is the sickle cell allele dominant (​S​) or
recessive (​s​)? Explain your reasoning. Include a Punnett Square in your answer.
The sickle cell allele illustrates some common complexities of genetics that we have ignored thus far. Read the
information in this box, and then answer questions 3 and 4.
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People who are ​homozygous​ for the sickle cell allele have sickle cell anemia, including pain and
organ damage due to blocked circulation and anemia (low red blood cell levels) due to more
rapid breakdown of red blood cells. People who are ​heterozygous​ for the sickle cell allele almost
never experience these symptoms. Therefore, the allele for sickle cell hemoglobin is generally
considered to be recessive and the allele for normal hemoglobin is generally considered to be
dominant.
However, a heterozygous person does ​not​ have exactly the same phenotype as a person who is
homozygous for the allele for normal hemoglobin. Specifically, people who are heterozygous for
the allele for sickle cell hemoglobin are less likely to develop severe malaria than people who are
homozygous for the allele for normal hemoglobin.
Malaria is caused by a parasite that infects red blood cells. The red blood cells of heterozygous
individuals have both sickle cell and normal hemoglobin. Malaria parasites are less able to
reproduce in red blood cells that have some sickle cell hemoglobin. This explains why people
who are heterozygous for the allele for sickle cell hemoglobin have less severe malaria infections
than people who are homozygous for the allele for normal hemoglobin.
3.​ Explain how the hemoglobin gene illustrates the following generalization:
A single gene often has multiple phenotypic effects.
4.​ Often, when geneticists investigate a pair of alleles, neither allele is completely dominant or completely recessive.
In other words, the phenotype of a person who is heterozygous for these two alleles is different from the phenotypes
of people who are homozygous for either allele. Explain how this general principle is illustrated by the sickle cell and
normal alleles for the hemoglobin gene.
Flower Color Genetics Lab
Objective
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Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a
population.
Background
A certain species of plant produces either bright red flowers or pure white flowers. In working out the
inheritance of a trait with contrasting forms such as flower color, it is important to determine which symbols will
be assigned to the alternative forms (alleles) of the genes for the trait (in this case, red and white). The first
letter for one of the alternative forms of the trait is generally used to represent the alleles for a trait. A capital
letter is usually assigned to the dominant allele, and a lowercase letter is assigned to the recessive allele. For
example, if ​R​ is used to represent red, then ​r​ would represent white. Or, if ​W​ is used to represent white, then
w​ would represent red. The pair of genes that determines a trait is called a g
​ enotype​. The genotype is
represented by the pair of letters that symbolizes the alleles present. When both genes in the pair are the
same, the genotype is said to be ​homozygous​. When the genes in a pair are different, the genotype is said to
be ​heterozygous​.
Purpose
In this activity, you will perform simulated crosses between red-flowered plants and white-flowered plants.
Based upon the preceding paragraph, identify and state the problem that needs to be solved before the
inheritance of flower color in this plant can be studied further.
To recall how the results of a cross are predicted, complete the following exercise. In cats, black coat color, ​B​,
is dominant to white coat color, ​b​. To predict the possible coat colors of the kittens that would result from a
cross between two heterozygous black cats (​Bb​ x ​Bb​), complete the following Punnett square.
Procedure
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In order to simulate crosses between plants with red or white flowers, you will use solutions to represent flower
color. The pink solutions represent plants with red flowers. The clear solutions represent plants with white
flowers. Assume that plants with a particular flower color may or may not be carrying a gene for alternate
flower color. When you mix the two solutions, the color of the resulting mixture represents a flower color that
could be observed among the offspring of two plants if you were to actually cross plants with flowers the same
colors as the solutions.
Caution: ​The solutions you will use in the following experiment contain chemicals that could damage your
skin, eyes or clothing. Follow the suggested safety precautions. Also, be aware that contamination will have
adverse effects on your data, pay attention and only mix solutions in designated containers. If you feel that
contamination has occurred, let your instructor know immediately. When you have finished your experiment,
all solutions may be rinsed down the sink drain.
1.​
2.​
3.​
​Obtain
8 small test tubes from the materials table. Label them 1-8.
​Obtain 1 mL of each of the solutions in the table below. B
​ e careful not to contaminate solutions!
​Record the “flower” color (​red or white​) of each to complete the table.
Color
Solution #1
Solution #2
Solution #4
Solution #5
Solution #7
4.​ ​Perform Cross #1:​ pour solution #1 and solution #2 into test tube #3; invert to mix. Record the
phenotypes (colors) of the parents and resulting offspring in the boxes below.
5.​ ​Perform Cross #2:​ pour solution # 4 and solution #5 into test tube #6; invert to mix. Record the
phenotypes (colors) of the parents and resulting offspring in the boxes below.
6.​ ​Based on the background information and the results of cross #1 and cross #2, which flower color is
dominant? Which flower color is recessive? Use the Punnett squares below to determine heredity of flower
color.
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Cross #1
Cross #2
7.​ ​Fill in the boxes below with the g
​ enotype​ of each flower based on your prediction above. If you
determined red to be the dominant flower color, use R/r to represent red/white flowers. If you determined white
to be the dominant flower color, use W/w to represent white/red flowers. ​If a genotype cannot be
determined with complete certainty, write both possible genotypes.
8.​ ​Test your prediction of the dominant flower color by performing Cross #3: p
​ our solution # 6 (test
tube #6) and solution #7 into test tube #8; invert to mix. Record the phenotypes (colors) of the parents and
resulting offspring in the boxes below.
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9.​ ​Fill in the boxes below with the g
​ enotype​ for Cross #3. ​If a genotype cannot be determined with
complete certainty, write both possible genotypes.
Conclusion
Write a paragraph explaining your initial question and hypothesis and whether or not your data supported or
refuted your initial ideas. Use examples from your data and analysis as evidence for your argument of the trait
type in this flowering plant. Include any revisions you made during the lab or revisions you would do if you
attempted this investigation again. Finally, discuss strengths and weaknesses of using this simulation model
for crossing flowering plants.
Soap Opera Genetics
Genetics to Resolve Family Arguments
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I. How could our baby be an albino?
Tiffany and Joe have just had a baby and are very surprised to learn that their baby is albino with very pale skin and
hair color. Tiffany‘s sister has come to visit Tiffany and the new baby, so Joe goes out to talk with his sister Vicky.
Did Tiffany have an affair?
Joe is very angry. He tells Vicky, "I think Tiffany had an affair with Frank! He’s the only albino we know. Obviously,
Tiffany and I aren't albino, so Frank must be the father."
1.​ Luckily, Vicky remembers her high school biology, so she explains that heterozygous parents can carry a recessive
allele for albinism. She draws a Punnett Square to show how two heterozygous parents with normal skin and hair
color could have an albino baby. Draw this Punnett Square. Use ​A​ for the dominant allele that results in normal skin
and hair color and​ a​ for the recessive allele that can result in very pale skin and hair color.
2. ​Joe is still mad and he doesn't understand Vicky's explanation. He says "You aren't even speaking English! What are
heterozygous parents? What's a recessive allele? And what's the connection between alleles and skin color?" Answer
his questions.
3.​ Once Joe understands this much, he asks for a better explanation of the Punnett square. Draw a new, more
complete Punnett Square that includes the genotypes of both parents, labels to indicate which symbols represent the
genetic makeup of eggs, sperm, or zygotes, thin arrows (​→​) to represent meiosis, and fat arrows (​⇒​) to represent an
example of fertilization.
4. ​Joe says "Okay, I'm beginning to understand, but what are zygotes? What's the connection between the zygotes in
the Punnett square and our baby?" Answer Joe's questions.
Why aren't more babies albino?
By now, Joe has calmed down and he is getting interested. He asks Vicky "If that’s how it works, it seems as though a
quarter of all babies should be albino. How come there are hardly any albino babies?"
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5. ​What explanation should Vicky give to answer this question?
Joe is starting to feel guilty for getting so mad. He says "Geez, I feel like a jerk. I should have known that Tiffany
would never cheat on me." Vicky responds, "That's okay. You were upset. Let's just forget about it."
Will Tiffany and Joe's next baby be albino?
Two years later, Tiffany is pregnant again, and she and Joe are discussing whether their second baby will be albino.
Tiffany thinks the baby probably will be albino, but Joe remembers Vicky's explanation, and he tells Tiffany, "No, our
second baby can't be albino because only one out of every four of our children should be albino. We already have one
albino child, so our next three children should not be albino."
6a.​ Is Joe right? Explain why or why not​.
6b.​ What is the probability that Tiffany and Joe's second baby will be albino?
6c. ​How do you know?
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II. Were the babies switched?
Two couples had babies on the same day in the same hospital. Denise and Earnest had a girl, Tonja. Danielle and
Michael had twins, a boy, Michael, Jr., and a girl, Michelle. Danielle was convinced that there had been a mix-up and
she had the wrong baby girl, since Michelle had light skin, while Michael Jr. and Tonja looked more like twins since
they both had dark skin.
Danielle insisted on blood type tests for both families to check whether there had been a mix-up. To interpret the
results of these tests, you will need to understand the genetics of blood types.
Genetics of Blood Types
The ABO blood type system is the major blood type classification system that determines which type of blood can
safely be used for a transfusion. The four blood types in the ABO system refer to different versions of carbohydrate
molecules which are present on the surface of red blood cells.
These different blood types result from
different alleles of a ​gene​ in the DNA that give the directions for making
different versions of a ​protein​ enzyme that puts
different types of carbohydrate molecules on the surface of red blood cells.
Allele
A
B
O
Gives the directions for making a version of the enzyme that:
puts type A carbohydrate molecules on the surface of red blood cells
puts type B carbohydrate molecules on the surface of red blood cells
is inactive; doesn't put either type of carbohydrate molecule on the surface of red blood cells
1.​ Each person has two copies of this gene, one inherited from his/her mother and the other inherited from his/her
father. Complete the following table to relate genotypes to blood types.
Genotype
AA
OO
AO
This person's cells make:
the version of the enzyme that puts type A carbohydrate molecules on the
surface of red blood cells.
the inactive protein that doesn’t put either type A or type B carbohydrate
molecules on the surface of red blood cells.
both the version of the enzyme that puts type A carbohydrate molecules on
the surface of red blood cells and the inactive protein
Blood Type
A
2.​ In a person with the ​AO​ genotype, which allele is dominant, ​A​ or ​O​? Explain your reasoning.
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3.​ For the genotypes listed below, which type(s) of enzyme would this person's cells make? What blood type would
the person have?
Genotype
Will this person's cells make the version of the enzyme needed to put this
carbohydrate on the surface of his/her red blood cells?
BB
Type A __ yes __ no;
Type B __ yes __ no
BO
Type A __ yes __ no;
Type B __ yes __ no
AB
Type A __ yes __ no;
Type B __ yes __ no
Blood Type
AB
Codominance​ refers to inheritance in which two alleles of a gene each have a different observable effect on the
phenotype of a heterozygous individual. Thus, in codominance, neither allele is recessive — both alleles are
dominant.
4.​ Which of the genotypes listed above results in a blood type that provides clear evidence of codominance? Explain
your reasoning.
Were the babies switched?
Now you are ready to evaluate whether Earnest and Denise's baby girl was switched with Michael and Danielle's baby
girl.
This figure shows the blood types of the families
if the hospital did not make a mistake.
This figure shows the blood types of the families if
Tonja and Michelle were accidentally switched.
5.​ One of the families shown is genetically impossible. Draw a Punnett square for each pair of parents to show how
three of these families are genetically possible and to identify which family has a child who could not possibly have
inherited her blood type from parents with the blood types shown.
6.​ Who are Tonja's parents? How do you know? Did the hospital make a mistake?
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Why do the twins look so different?
Now, Danielle wants to know how her twins could look so different, with Michelle having tan skin and Michael Jr.
having dark skin. First, Danielle needs to understand that there are two types of twins. Identical twins have exactly
the same genes, since identical twins originate when a developing embryo splits into two embryos.
7.​ How do you know that Michelle and Michael Jr. are not identical twins?
Michelle and Michael Jr. are fraternal twins, the result of two different eggs, each fertilized by a different sperm.
These different eggs and sperm had different alleles of the genes for skin color. Therefore, Michelle and Michael Jr.
inherited different alleles of these genes, so they have different skin colors.
Genotype
Phenotype ​(skin color)
To begin to understand how Michelle could have tan skin
BB
dark brown
and her twin brother, Michael Jr., could have dark skin, we
Bb
light brown
will consider two alleles of one of the genes for skin color.
Notice that, for this gene, a heterozygous
bb
tan
individual has an intermediate phenotype, halfway between the two homozygous individuals.
When the phenotype of a heterozygous individual is intermediate between the phenotypes of the two different types
of homozygous individual, this is called ​incomplete dominance​.
8a.​ Explain how incomplete dominance differs from a dominant-recessive pair of alleles. (Hint: Think about the
phenotypes of heterozygous individuals.)
8b.​ Explain how incomplete dominance differs from co-dominance.
9.​ The parents, Michael and Danielle, both have light brown skin and the ​Bb​ genotype. Draw a Punnett square and
explain how these parents could have two babies with different color skin – one dark brown and the other tan.
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Obviously, people have many different skin colors, not just dark brown, light brown, or tan. One reason for
the many different skin colors is that skin color is influenced by multiple genes with multiple alleles. Scientists
have found that:
● Different skin colors result from differences in the types and amounts of the pigment melanin in skin
cells.
● Several different proteins influence the production and processing of melanin molecules in skin cells.
● Different alleles of the genes that code for these proteins result in different skin colors.
Environmental influences also affect skin color. For example, exposure to sunlight can change the activity of
genes that influence skin color and increase the amount of melanin in skin cells.
This flowchart summarizes the multiple genetic and environmental influences on skin color.
10.​ This information indicates that the chart on the previous page is oversimplified. Multiple factors influence
skin color, so two people who both have the ​Bb​ genotype can have different skin colors. For example,
Hernando and Leo both have the ​Bb​ genotype, but Hernando’s skin is darker than Leo’s. Explain two possible
reasons why Hernando and Leo have different skin colors.
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III. I don't want to have any daughters who are color blind like me!
Awilda and Frank at Breakfast
Awilda: Are you sure you want to wear that new shirt to work today? A green and red shirt like that would be
better for Christmas, not for St. Patrick's Day.
Frank: Oh no! Not again! I really thought this shirt was just different shades of green. Where's the red?
At Dinner That Night
Frank: We should try to find a way to make sure we only have sons, no daughters. I don't want to have any
daughters who might be color blind like me. Color blindness would be a big problem for a girl.
Awilda: Remember, the doctor said that he doesn't think that any of our children will be color blind.
Frank: I don't see how he can be so sure about that. I'm color blind, so some of our children should be color
blind like me.
Awilda: The doctor said that, since no one in my family was color blind, I almost certainly do not have the
allele for color blindness, so none of our children will be color blind.
Frank: That doesn't make any sense. Neither of my parents is color blind, but I'm color blind. I think that our
children will be more likely to be color blind since they will have a color blind father.
Answer these questions to help Awilda explain to Frank why none of their children will be color blind.
1a.​ What are the genotypes of Frank and Awilda? (Since the allele for color blindness is located on the X
chromosome, use the symbol X​cb​ for an X chromosome with the recessive allele for color blindness and X​N​ for
an X chromosome with the dominant allele for normal color vision. The Y chromosome does not have this
gene, so it is represented by Y.)
Frank _______
Awilda _______
1b.​ Draw a Punnett square for this couple and their children.
1c.​ Explain why none of their children will be color blind.
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Frank: Okay, I guess I don't have to worry about any of our children being color blind, but what about our
grandchildren? Couldn't some of them be color blind, especially our granddaughters?
Awilda: Well, some of our grandchildren could be color blind, but I've heard that boys are more likely than girls
to be color blind.
Frank: I disagree. Girls have more X chromosomes than boys, so girls should be more likely to be color blind.
Answer the following questions to explain why Awilda and Frank’s grandsons are more likely than their
granddaughters to be color blind.
2a.​ What are the possible genotypes for Awilda and Frank's children?
Awilda and Frank's sons _______
Awilda and Frank's daughters _______
2b. ​Draw a Punnett square for each couple in the chart below.​ ​In each Punnett Square, circle each boy and use
arrows to indicate any color blind offspring.
Punnett square if one of Awilda and Frank's
daughters marries a man who is color blind
Punnett square if one of Awilda and Frank's
daughters marries a man who is ​not​ color blind
2c.​ Explain why Awilda and Frank's grandsons are more likely than their granddaughters to be color blind.
3. ​Explain why having two X chromosomes decreases a woman’s risk of color blindness, instead of increasing
her risk.
4. ​Remember that Frank is colorblind, but neither of his parents are colorblind. Which Punnett square shows
how two parents who are not colorblind could have a color blind son?
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Genetic Engineering and Transgenic Organisms
Answer all questions in complete sentences!!!!!
Before you begin:
1.​ ​In your own words, define the term herbicide:
2.​
​In
your own words, define the term resistant:
http://www.pbs.org/wgbh/harvest/engineer/transgen.html
3.​ ​What will you be producing in this animation?
4.​
​Where
will the new gene come from?
5.​
​What
is Bt?
6.​
​What
does this gene code for?
7.​
​What
will be special about this new crop?
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Follow the steps and answer the questions as you go.
Step One:
8.​ ​What is a vector?
9.​
​How
many genes were added?
Step Two:
10.​ ​In your own words, what is the purpose of Agrobacterium?
Step Three:
11.​ ​What is the purpose of growth medium?
Step Four:
12.​ ​What is the purpose of this step?
Step Five:
13.​ ​What is the purpose of this step?
Step Six:
14.​ ​What is the purpose of this step?
Step Seven:
15.​ ​How will scientists know if the new gene is working in the mature plant?
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Go to: ​ ​http://www.pbs.org/wgbh/harvest/coming/coming.html
16.​ ​Click on any 5 different materials found at the table in any order. Write the name of the item you chose
and then explain how and why it is being genetically modified.
a.___________________________
Why?
b.___________________________
Why?
c.___________________________
Why?
d.___________________________
Why?
e.___________________________
Why?
Go to:
http://www.treehugger.com/corporate-responsibility/first-drug-made-from-genetically-engineered-animals-appro
ved-by-fda.html
17.​ ​What was the first medicine produced by a GMO?
18.​ W
​ hat organism was modified?
19.​ W
​ here was the recombinant DNA placed?
20.​ W
​ here was the new medicine produced?
21.​ W
​ hat does the medicine do?
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Go to: ​ ​http://news.bbc.co.uk/2/hi/science/nature/889951.stm
22.​ ​Explain how and why scientists have genetically modified these goats.
Go to: ​ ​http://abcnews.go.com/Health/story?id=117204&page=1
23.​ ​Name three ways that scientists could genetically modify organisms to use as weapons.
a.___________________________________________________________________________
b.___________________________________________________________________________
c.___________________________________________________________________________
Go to:
http://www.mnn.com/green-tech/research-innovations/photos/12-bizarre-examples-of-genetic-engineering/envir
opig
24.​ ​Use the arrows to go through the gallery. Read the explanations on the side and classify the organisms in
the chart below. You will have 10 filled in when you are finished.
Important for the Environment
Important for Humans
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Go to: ​ ​http://www.pbs.org/wgbh/harvest/exist/
Scroll to the bottom and click on “View all 12 arguments”
25.​ ​Read through the arguments for and against GM foods. Give 5 positives and 5 negatives of GMO’s in a
t-chart below. Be thorough.
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Units 3 & 4 Reflection
A. How does each lab/activity exemplify the learning targets for the unit? Be specific about each learning
target and use the dos and don’ts suggestions!
82
B. What were you able to learn by completing the labs/activities? Again, be specific about each learning
target and use the dos and don’ts suggestions!
83
C. How did the labs/activities compare and contrast to each other? Again, be specific about each learning
target and use the dos and don’ts suggestions!
84
D. In which labs did you experience trouble? Again, be specific and use the dos and don’ts suggestions!
85
E. How does this unit of work relate to real life situations? Again, be specific and use the dos and don’ts
suggestions!
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Article Rationale & Summary
Article Title: ​____________________________________________________________________________
Author(s): ​_____________________________________________________________________________
Source: ​________________________________________________________________________________
Summary: ​Summarize the main points of the article in 4-6 sentences.
Rationale for inclusion in this unit: ​How does the material in the article relate to what was learned/studied in
this unit? Include a detailed description of at least 3 different specific examples. Again, be specific about each
connection and use the dos and don’ts suggestions!
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(Copy of Article)
88
Personal Choice
89
Rationale for Personal Choice
90