Download SCIENCE - GENETICS

G-3
GENETICS
The study of how organisms inherit their traits
-PART TWOTEAM E SCIENCE
May/June 2008
Name: ________________________________
GENETICS
Essential Questions and Vocabulary
-PART TWO***********************************************************************************************
3. What are the characteristics of the human genome (i.e. genetic material)?
SOMATIC CELLS
SEX CELLS
SPERM
SEX-LINKED TRAITS
FERTILIZATION
MEIOSIS
EGG
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4. What is the structure of DNA?
Deoxyribonucleic acid
DOUBLE HELIX
NITROGEN BASES
Guanine
Cytosine
Thymine
Adenine
PHOSPHATE and
SUGAR MOLECULES
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5. How are proteins and DNA synthesized in the cell?
MESSENGER RNA (mRNA)
Uracil
TRANSFER RNA (tRNA)
PROTEIN
AMINO ACIDS
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6. Can you apply and explore GENETICS?
SEE ATTACHED ARTICLE and JOURNAL ASSIGNMENT #17!
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SCIENCE - GENETICS
THE HUMAN GENOME
Essential Question #3
NOTES:

The HUMAN genome is the set of genetic material that humans have in all their cells.

The HUMAN genome consists of 46 chromosomes in all --- or 23 pairs.

One pair of those 23 pairs of chromosomes determines the sex of the human offspring. This
chromosome pair (aka the sex chromosomes) is expressed as XX for female offspring and XY for male
offspring (notice that there is not a lower case letter representing a recessive allele!). According to the
Punnett Square method then, the chance of having a boy or girl is ALWAYS 50-50! Prove it below!
Phenotype/Genotype XX (girl):
____ or ___%
Phenotype/Genotype XY(boy):
____ or ___ %

There are GENERAL CATEGORIES of cells for humans: SOMATIC (i.e. body) cells and SEX (i.e.
gametes) cells.
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Somatic cells have those 23 pairs of chromosomes in them. They are referred to as being DIPLOID.

You also have sex cells. These are the egg
and the sperm
; they are also referred to
as GAMETES. They have 23 chromosomes ONLY. They have half as many chromosomes as the
somatic (body) cells: 23 chromosomes …NOT 23 chromosome pairs!!!

When the sex cells (GAMETES) of humans combine, the process is called FERTILIZATION. The 23
chromosomes from each gamete join to make the 23 pairs of chromosomes in a complete cell called a
ZYGOTE that is capable of going through mitosis to form more cells. Cell division keeps going on…cells
become specialized…and eventually you have a human being that is ready to be born and ready to
continue growing!

To make IDENTICAL TWINS, one egg is fertilized and it divides into two SEPARATE zygotes. To make
FRATERNAL TWINS, two different eggs are fertilized by two different sperm, forming two SEPARATE
zygotes from the start!

Sex cells are formed in a special process called MEIOSIS. It starts with a “normal” body or somatic cell
going through mitosis. THEN, the two new daughter cells with the 23 chromosome PAIRS in them that
are produced from mitosis go through one more cell division…BUT THERE IS NO REPLICATION OF
THEIR DNA (there is only one interphase!). As a result, the chromosome pairs of the two cells get
separated and the two cells become four cells – each cell has only 23 chromosomes or half the amount of
chromosomes as the somatic cells (this is called being HAPLOID)! It looks like this…

Some traits are called SEX-LINKED traits. These RECESSIVE traits are genes that are USUALLY
located on the X chromosome (hence the name sex-linked because they are linked to a sex
chromosome). The Y chromosome may SOMETIMES have a sex-linked trait on it; for the most part the
Y chromosome only has a gene for “maleness” on it.
Sex-linked traits show themselves more often in males. This is because the usual carrier of the
sex-linked trait is the X chromosome; since males have an X and a Y chromosome, the Y chromosome
will not carry a gene to match and influence the X chromosome sex-linked trait. On the other hand,
since a female has two X chromosomes, the X chromosome with the sex-linked RECESSIVE trait may
be masked if the other X chromosome has a matching DOMINANT gene for that trait. As a result,
females may not have the phenotype for the sex-linked trait but instead may be ONLY a CARRIER of
the trait because they contain one X chromosome with the recessive sex-linked trait gene.
Colorblindness is a common example of a sex-linked trait that is carried on the X chromosome. Let’s try
it out in a Punnett Square below. To show a sex-linked trait, we use a capital or lower case letter
superscript or exponent to represent the trait on the sex chromosome; the lower case letter,
because sex-linked traits are recessive, represents the presence of the sex linked trait. For
colorblindness, XC (the X chromosome with a capital exponent “C”) would represent a chromosome
WITHOUT the recessive trait for colorblindness and Xc (the X chromosome with a lower case
exponent “c”) would represent a chromosome WITH the recessive trait for colorblindness.
ASSUME THAT…the mother has a recessive gene for colorblindness but does not have
colorblindness. In other words, she is a CARRIER. The father does not have color blindness.
OUTCOME
Females who
ARE
colorblind
%
PROBABILITY
(% and fraction)
fraction
Female
CARRIERS
%
fraction
Females who
are NOT
CARRIERS and
do NOT have
colorblindness
%
fraction
Males who
ARE
colorblind
%
faction
Males who are
NOT
colorblind
%
fraction
Gimme “5”!
Five important concepts that I learned about the
Human Genome are:
1)
2)
3)
4)
5)
PRACTICE QUESTIONS ON THE HUMAN GENOME AND MEIOSIS
DIRECTIONS: Use the information from the notes on the HUMAN GENOME AND MEOSIS to
answer the following questions. For the multiple choice questions, place the letter of the best answer
in the blank provided. The last question requires you to construct a Punnett square for a sex-linked
trait.
___1) Which of the following statements is true about the human genome?
a) In females, the somatic cells have 23 chromosomes and the sex chromosome is XY.
b) In males, the somatic cells have 23 chromosomes and the sex chromosome is XX.
c) In females, the sex cells have 23 chromosomes and the sex chromosomes can only be Y.
d) In males, the sex cells have 23 chromosomes and the sex chromosomes can be either X or Y.
___2) What are the names of sex cells of a male and female called and what do they look like?
a) Female – egg
Male – sperm
b) Female – sperm
Male – egg
c) Female – egg
Male – sperm
c) Female – sperm
Male - egg
___3) Which of the following are the two categories of cells in the human body?
a)
b)
c)
d)
body and somatic
sex and skin
somatic and sex
somatic and automatic
___4) The process in which an egg and sperm gametes unite:
a) is called fertilization and results in a zygote with 23 chromosomes.
b) is called fertilization and results in a zygote that is capable of becoming a human.
c) is called fertilization and results in a zygote that will go through meiosis.
d) All of the above are correct.
___5) Meiosis and mitosis differ in that:
a) there are four cells produced in mitosis and the daughter and parent cells have the same
amount of chromosomes.
b) mitosis can only happen to sex cells.
c) there are two cell divisions in meiosis and the gamete (sex cells) have half the amount of
chromosomes as the parent cells.
d) DNA does not get replicated in meiosis.
___ 6) Sex-linked traits:
a)
b)
c)
d)
occur mostly on the X chromosome and are dominant.
occur only on the X chromosome and are dominant.
occur mostly on the Y chromosome and are recessive
occur mostly on the X chromosome and are recessive.
___ 7) Baldness is an X chromosomes sex-linked trait. To represent a FEMALE who is hybrid for
baldness (has gene but is not bald) and a MALE that is purebred for baldness (is bald), the correct
abbreviations would be:
a) FEMALE – XbXb MALE – XbYb
b) FEMALE – XBXb MALE – XBYb
c) FEMALE – XBXb
MALE – XbY
d) FEMALE – XBYb
MALE – XbXb
8) Hemophilia is disease in which a person’s blood will not clot effectively or will not clot at all.
Clotting is the process that occurs to stop you from bleeding when you get cut. This disease is
a sex-linked recessive trait on the X chromosome.
Construct a Punnett square based on a mother who has hemophilia and a father that does not.
OUTCOME
Females who
HAVE
hemophilia
%
PROBABILITY
(% and
fraction)
fraction
Female
CARRIERS
WITHOUT
hemophilia
%
fraction
Females who
are NOT
CARRIERS and
do NOT have
hemophilia
%
fraction
Males who
HAVE
hemophilia
%
faction
Males who do
NOT have
hemophilia
%
fraction
SCIENCE - GENETICS
THE STRUCTURE OF DNA
Essential Question #4
NOTES:

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







As you already know, DNA is Deoxyribonucleic Acid. It is the molecule that determines the
genetic makeup – the TRAITS – of an organism as well as the functions of the cell.
The DNA name comes from the deoxyribose sugar molecule that it contains – DEOXYRIBO –
and the fact that it is located in the nucleus – NUCLEIC – and the fact that is acidic in nature –
ACID.
Our knowledge about the structure of DNA is based on the work of four scientists during the late
1950’s and early1960’s - James Watson, Francis Crick, Maurice Wilkins, and Rosalind Franklin.
The molecule of DNA is structured like a twisting staircase.
The sides of the staircase are made up of a group of phosphate and sugar (deoxyribose)
molecules (containing the elements of phosphorus, hydrogen, and oxygen).
The steps of the staircase are formed by pairs of substances called nitrogenous bases that
contain the element nitrogen in addition other elements.
There are FOUR different nitrogenous bases: ADENINE, GUANINE, CYTOSINE, and THYMINE.
They are abbreviated with the letters A, G, C, and T.
Nitrogenous bases combine to form amino acids – these are the building blocks of
PROTEIN! Protein is essential to our body – it is what helps to build and repair cells.
To create the complete staircase, nitrogen bases pair up with one another. A always pairs with
T and G always pairs with C. Think: Amy (Miss P) Told me Genetics is Cool! The different
combinations and the order of these combinations along the steps of the staircase of DNA that
can be created from these pairs determine the traits of an organism as well as the functions of a
cell. Only four substances determine ALL the traits of ALL the organisms on the planet!
The DNA molecule looks like this:
Gimme “5”!
Five important concepts that I learned about DNA Structure:
1)
2)
3)
4)
5)
PRACTICE QUESTIONS ON DNA STRUCTURE
DIRECTIONS: Use the information on the previous page to help you answer the following questions.
Place the correct answer in the blank next to each question.
___ 1) DNA:
a)
b)
c)
d)
contains phosphate and sugar molecules along the sides of its staircase structure.
looks like a spiral staircase and is made up of water and hydrogen molecules.
looks like a spiral staircase and has “steps” made out of nitrogen base pairs.
a and c are correct.
___ 2) Which of the following correctly matches the nitrogen base pairs?
a)
b)
c)
d)
guanine with cytosine and thymine with adenine.
guanine with adenine and thymine with cytosine.
guanine with thymine and cytosine with adenine.
guanine with adenine and thymine with guanine.
___ 3) Nitrogen bases combine to form:
a)
b)
c)
d)
amino acids which are the building blocks of proteins.
amino acids which are the building blocks of carbohydrates.
amino acids which are the building blocks of fats.
all of the above.
___ 4) Protein is important to our body because:
a)
b)
c)
d)
it helps our body to function.
It helps our body to build cells.
It helps our body to repair cells.
all of the above.
___ 5) The scientists responsible for creating our understanding of the DNA structure were:
a)
b)
c)
d)
Francis Crick.
Rosalind Franklin.
James Watson.
All of the above.
___ 6) Label the DNA Structure below. Use the terms: “Nitrogen Base Pairs” and “Sugar and
Phosphate Molecules”
SCIENCE - GENETICS
DNA SYNTHESIS
Essential Question #5
NOTES:


When it comes time for a parent cell to divide, the DNA of that cell has to be replicated so that the
daughter cells are the identical to the parent cell.
DNA is replicated during interphase in a three step process.
STEP 1. DNA “UNZIPS”
The DNA molecule splits in half and the
the nitrogenous base pairs separate.
STEP 2. NEW NITROGEN PAIRS ATTACH
Free-floating nitrogenous bases in the
nucleus attach themselves to their
matching nitrogenous base partners on
each of the sides of the split DNA
staircase.
STEP 3. TWO IDENTICAL DNA MOLECULES
ARE
COMPLETED
All of the nitrogenous bases on the steps
of the DNA staircase have been
paired with NEW nitrogenous base pairs.
The result? TWO IDENTICAL DNA
MOLECULES THAT BECOME JOINED
AT THE CENTROMERE AND ARE READY
FOR MITOSIS!
Gimme “5”!
Five important concepts that I learned about DNA Synthesis
are:
1)
2)
3)
4)
5)
REVIEW QUESTIONS ON DNA REPLICATION
DIRECTIONS: Use the information on the previous page to help you answer the following questions.
Place the correct answer in the blank next to each question.
___ 1) Suppose the nitrogen base pattern along one side of a DNA molecule was TTAGCCT. What
would the other side of the DNA molecule be like?
a)
b)
c)
d)
AAUCGGA
UUTATTU
UUTCGGA
AATCGGA
___ 2) During what phase of cell division does DNA replication occur?
a)
b)
c)
d)
prophase
interphase
anyphase
telephase
___ 3) The steps of how DNA gets replicated are:
a) the DNA unzips itself, two identical DNA molecules are formed, and new nitrogen bases
attach themselves.
b) the DNA unzips itself, new nitrogen bases attach themselves, and two identical DNA
molecules are formed.
c) the DNA unzips itself, mRNA attaches to the DNA, and two identical DNA molecules are
formed.
d) new nitrogen bases attach themselves, the DNA unzips itself, and two identical DNA
molecules are formed.
SCIENCE - GENETICS
PROTEIN SYNTHESIS
Essential Question #5
NOTES:





DNA is not only important because it carries genetic and hereditary material, but it is also important
because it helps in the making of PROTEINS for an organism. This process is called PROTEIN
SYNTHESIS.
Proteins are they themselves important because they are necessary for building and repairing cells and
controlling bodily functions, as well as being the ingredients that make up hormones and enzymes.
AMINO ACIDS are the building blocks of proteins. There are a total of 20 different amino acids in your
body!
RNA (ribonucleic acid) is a molecule that gets formed by the ribosomes and it is important in helping
to make proteins for the cell.
RNA comes in two forms: and messenger RNA (mRNA) and transfer RNA (tRNA).
Gimme “5”!
Five important concepts that I learned about Protein
Synthesis are:
1)
2)
3)
4)
5)
PRACTICE QUESTIONS ON PROTEIN SYNTHESIS
DIRECTIONS: Use the information on the previous page to help you answer the following questions.
Place the correct answer in the blank next to each question.
___ 1) Transfer RNA:
a)
b)
c)
d)
is abbreviated as TRNA.
attaches itself to the DNA molecule in protein synthesis.
reads the code of mRNA and brings amino acids together to form protein chains.
All of the above are correct.
___ 2) Messenger RNA:
a)
b)
c)
d)
is abbreviated as MRNA and helps in protein synthesis in cells.
carries the information about protein synthesis from the nucleus to the cytoplasm.
is made up of a nigtrogen base code.
b and c are correct.
___ 3) Amino acids:
a)
b)
c)
d)
are the building blocks of proteins.
are composed of three nitrogen bases.
are found in the DNA molecule.
a and b are correct.
___ 4) Uracil is a nitrogen base that:
a)
b)
c)
d)
is found in mRNA.
replaces adenine in RNA.
is found in DNA.
replaces cytosine in mRNA.
___ 5) What are the different types of RNA that are involved in protein synthesis?
a) message RNA and transport RNA.
b) messenger RNA and transfer RNA.
c) message RNA and transfer RNA.
d) messenger RNA and transport RNA.
___ 6) During the synthesis of protein, tRNA:
a)
b)
c)
d)
creates amino acids to form protein chains.
gathers amino acids together to form protein chains.
interprets a code directly from DNA.
b and c are correct.
___ 7) Which of the following correctly pairs the molecules with their functions?
a)
b)
c)
d)
RNA carries the genetic information of an organism and helps in making proteins.
tRNA helps to synthesize protein by carrying a code of nitrogen bases from DNA to mRNA.
mRNA helps to synthesize amino acids by translating codes of nitrogen bases from mRNA.
DNA carries the genetic information of an organism and helps in making proteins.
___ 8) Proteins:
a)
b)
c)
d)
are made from chains of 10 different types of amino acids.
help in the repairing and building of cells.
are an important part of the endocrine system.
b and c are correct.
___ 9) The three-letter codes that help a tRNA molecule know when to begin building a protein
chain and when to stop are:
a)
b)
c)
d)
UAA, which means start, and UAG, UGA, and AUG, which mean stop.
UAG, which means start, and UGA, AUG, and UAA, which mean stop.
UGA, which means start, and AUG, UAA, and UAG, which mean stop.
AUG, which means start, and UAA, UAG, and UGA, which mean stop.
___ 10) What are the correct steps (in order!) of protein synthesis?
a) The DNA molecule unzips itself, new nitrogen base pairs attach to form mRNA, and the DNA
molecule zips back up.
b) The DNA molecule unzips itself, new nitrogen base pairs attach to from mRNA, and tRNA
makes amino acids.
c) The DNA molecule unzips itself, new nitrogen base pairs attach to form mRNA, and tRNA
reads the nitrogen base code from the mRNA.
d) The DNA molecule unzips itself, new nitrogen base pairs attach to form tRNA, and mRNA links
amino acids together to form protein chains.
___ 11) If a DNA molecule has a pattern of nitrogen bases of TTAGCCT, what pattern of nitrogen
bases would a mRNA molecule that came from this DNA molecule have?
a)
b)
c)
d)
AAUCGGA
UUTATTU
UUTCGGA
AATCGGA
SCIENCE - GENETICS
APPLYING AND EXPLORING YOUR NEW KNOWLEDGE
Essential Question #6
ASSIGNMENT:
Journal #17
June 2008
Applying and Exploring Your NEW “Genetical” Knowledge
You have just learned a great deal about genetics. By now you should be able to:

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

explain the “who and what” of the foundation of genetics.
create and interpret the Punnett Square.
describe the make up of the human genome.
illustrate and define the structure of DNA.
generalize the steps of DNA and protein synthesis.
(These are the concepts you need to know for the genetics quiz!)
So, why not apply and explore some of this new knowledge? Come on, show off your “genetical” know-how
and do ONE of the following tasks in the form of a journal entry. Before you start your entry, make sure to
state which task you have chosen.
THIS ASSIGNMENT IS DUE:________________________________!
1. CHOICE #1 – “Bah, bah CLONED sheep have you any DNA?”
Read the attached article on cloning. Write a 3 paragraph response (i.e. intro, body, and conclusion) to the
article. Tell what you learned about cloning and whether or not you think it is an area of research that
scientists should pursue. Support your thoughts with details from the article. WARNING – it’s a tough
article but it’s definitely worth a try!
2. CHOICE #2 – “The traits around you”
i.
ii.
iii.
Make a chart on your computer or on a piece of paper like the one below. Label the first column “Trait”,
the second column “Dominant Trait”, and the third column “Recessive Trait.”
Observe the human characteristics and traits in the world around you.
Fill up each column with as many GENE PAIR TRAITS as you can. Shoot for one journal page in
length. An example to get you started is listed in the first row underneath the column titles in the chart
below.
TRAIT
HAIR COLOR
iv.
v.
DOMINANT TRAIT
BROWN HAIR
RECESSIVE TRAIT
BLONDE HAIR
You can repeat traits if you want to by using different dominant and recessive pairs.
After you finish your data chart, answer these questions:
a)
b)
c)
d)
WHY were you able to predict a trait to be dominant or recessive?
Were there any traits that you had difficulty in predicting to be dominant or recessive?
Were there any traits that you thought would be dominant but were recessive or vice versa?
What traits, if any, appeared to be a result of incomplete dominance, codominance, or a mutation?
3. CHOICE #3 – “Oh, DEER!”
Read the following TRUE story about Mrs. P and her “lucky friend.” Use the story, your new “genetical”
knowledge, and, if you wish, background research via the internet to perform the task that follows.
Before Mrs. P was married, she lived in Yorktown and would often get up early in the morning to
go for a run along the bike path that was close to her house. She liked to go running on the bike
path because it went through the woods and it gave her the chance to be “one with nature.”
When Mrs. P is “one with nature,” she finds herself in a state of peace and perfect well-being; in
other words, she’s truly “in the moment.” 
(Please take a break from your reading and do a little meditation “OHM” in honor of the mood she
was usually in during her bike paths runs.)
During her bike path runs she kept her eyes open for different forms of wildlife. She often hoped
to see something different on her runs – something different from the usual squirrel, robin, crow,
chipmunk, rabbit, or brown deer.
LUCKY for her, she often did see something different…she had a special, unique, amazingly
different “friend” that she got to see more often than not on her morning runs through the
wilderness…
This special “friend” was always in the same place. Just past the railroad bridge that allows the
bike path to go over the Croton Reservoir there was a densely wooded area. In that area, on top
of a raised portion of ground, her “friend” always waited to greet her.
The first time she saw her “friend” she was worried that something was really “wrong” with her
head (there is something “wrong” with her head, as you already know, but this sight made her
think there was something REALLY, REALLY wrong with her head ).
But, upon seeing it several mornings and doing some scientific investigation to check out why her
“friend” was so different and amazing, she knew that she was not really THAT crazy. She is now
glad that she “met” this friend because it has given her some really cool GENETIC information to
challenge her 7th grade science students with.
And who was her friend? Mrs. P’s “friend” was a WHITE deer. Yes, a WHITE deer. A WHITE –
not a BROWN – deer. OH, DEER! A WHITE instead of a BROWN DEER!?!?
Mrs. P referred to friend as HER lucky white deer. She looked forward to seeing it when she ran
the bike path and she often thought that it was a sign of something good…a sign of luck and
safety in her life…like something was watching over her and protecting her!
YOUR TASK:
So, “DEAR” students, now it’s up to you to figure out the reason behind the strange appearance of Mrs. P’s
WHITE “DEER.”
 Explain in a paragraph WHY Mrs. P’s Lucky deer is WHITE instead of BROWN. Ask yourself, “What do
I think genetically happened to cause this amazing and beautiful phenomenon to occur?”
 Remember to use your own “genetical” knowledge and, if you wish, some background research
via the internet, to complete this challenge.
 Support your explanation with evidence and reasoning!