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Biology 30
Morinville Community
High School
Unit 4: Molecular Genetics
Name: ______________
2
Molecular Genetics Unit Outline
Chapter 1 8 tex t p. 6 22 -6 71
Key Concept A: DNA structure and the historical events
that lead to it’s discovery
A1. Isolating DNA as the hereditary material: Avery,
MacLeod, McCarty & Hershey and Chase
A2. Chemical Components of DNA & Chargaff’s Rule
A3. 3D Structure of DNA: Franklin, Watson, and Crick
Key Concept G: Diagnosis and Treatment of Genetic Disorders
G1. Genetic Counseling
G2. Prenatal Diagnosis
G3. Genetic Screening
G4. Treating Human Genetic Disorders
MOLECULAR GENETICS UNIT EXAM
Key Concept B: DNA Replication
B1. Semi-Conservative Replication of DNA
Key Concept C: Protein Synthesis
C1. Genes and the Genetic Code
C2. The nature of RNA & Amino Acids
C3. Transcription
C4. Translation
C5. Control of Gene Expression
Key Concept D: Mutations
D1. Causes & Severity of Mutations
D2. Types of Mutations
• Same-, Non-, and Mis-Sense
• Point Mutations
• Chromosome Mutations
• Chromosome Number Mutations & Karyotypes
Key Concept E: Genetic Technlogoy
E1. Restriction Enzyme s and Ligases
E2. Gel Electrophoresis and DNA Fingerprinting
E3. PCR
Key Concept F: Biotechnology Products
F1. Transgenic Bacteria (Gene Cloning)
F2. Transgenic Plants & Animals
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Key Concept A: DNA Structure and the historical events that lead to it’s discovery (p. 622-630)
A1. Isolating DNA structure and the historical
events that lead to it’s discovery p. 622-625
Introductory Activity: Extracting DNA
Purpose
Notes
Complete the following table to identify the contribution that each
of the following made to the discovery of DNA as the hereditary
material:
Scientist
Friedrich
Miescher
Discovery
Year
The purpose of this activity is to develop an understanding for the
structure of DNA at a molecule level and to observe DNA that has been
extracted from fruit. It is important therefore to follow the instructions
carefully & ask questions where necessary.
DNA Extraction
1. Put a ¼ strawberry or slice of banana into a sandwich bag and
close.
2. Thoroughly mush up the fruit, getting rid of all the big chunks,
leaving only liquid pulp.
3. While the fruit is being mixed, measure out 10 ml of lysis
solution. MEASUREMENTS NEED TO BE EXACT USING
GRADUATED CYLINDER.
Frederick
Griffith
Oswald
Avery, Colin
MacLeod,
and Maclyn
McCarty
Alfred
Hershey and
Martha
Chase
4. Add 10 ml of lysis solution to the fruit in the bag, close and mix
by gentle inversion and squishing. Mix for 5 minutes. Note: try
to avoid creating too much foam.
5. Place cheesecloth into a funnel and pour the fruit solution
through the cheesecloth, collecting the fruit liquid solution in the
large test tube. The cheesecloth should filter out the chunks.
6. Tilt the test tube and slowly add 10 ml of 95% ethanol along the
surface of the fruit solution and watch the DNA extract! After a
minute, plug the test tube with a stopper and mix by inversion a
few times to collect the remaining DNA from the fruits solution.
The DNA will look like a white bubbly glob!
7. Discard solid waste products into garbage, and liquids down the
drain.
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A2. Chemical Components of DNA and Chargaff’s
Rule p. 626-628
DNA is two long strands of nucleotides that are bound together in a spiral
shape called a ___________________________________________.
Voc abular y

DNA is composed of individual units called
______________________________

Each nucleotide consists of the following three molecules:
1.
Explain in your own words the contribution each of the following
scientists made in the discovery of the Double Helix:
2.
3.
Edwin Chargaff:

Draw a DNA Nucleotide:
Rosalind Franklin:
Complete the following table:
Type of Nitrogen
Examples
Base
1. ____________
Purines
2. ____________
Number of
Rings
James Watson and Francis Crick:
3. ____________
•
•
4. ____________
•
Pyramidines
The two DNA strands are anti-parallel
Sugar-phosphate backbones on the outside with the paired
nucleotide bases on the inside
The phosphate end of the chain is referred to as the 5’ end. The
opposite end is the 3’ end.
5
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Thought Lab: DNA Deductions
Edwin Chargaff discovered that the nucleotide composition of
DNA varies from one species to another. However, the
nucleotide composition always follows certain rules. This
constant relationship became known as Chargaff's rule: the
amount of adenine is equal to the amount of thymine, and the
amount of cytosine is equal to that of guanine.
i) Label a hydrogen bond on the diagram.
j) Label a phosphate group on the diagram.
k) Label a deoxyribose sugar on the diagram.
Pre-lab questions
Use the molecule to the right to answer the following
questions.
a) What is the number of base pairs illustrated in the molecule
to the right?
b) How many base pairs long is this DNA molecule?
c) What is the number of nucleotides shown in the diagram?
d) How many different nucleotides are there in the diagram?
e) What percentage of the nitrogen bases are adenine?
Without calculating, what percent must be
thymine?
f) If a DNA molecule contains 17.5% cytosine molecules, then
what percentage must be thymine molecules? Show your work.
g) How many hydrogen bonds hold together adenine and
thymine?
h) How many hydrogen bonds hold together cytosine and
guanine?
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Procedure – Complete the following on a separate sheet of
paper
1. Copy the following table. Imagine that you are analyzing a
DNA sample from the liver tissue of newly discovered species of
mouse. Use the information in the table below to complete the
nucleotide composition of your sample that will be 10 base pairs
long.
Nucleotide
Bases
adenine
cytosine
guanine
thymine
Percentage
in DNA
sample
Number
present
in a
molecule
10 bp long
Number
present
along one
side of the
double
helix
Analysis
1. Would the nucleotide composition of mouse liver tissue be different
from a second DNA sample from the muscle tissue of the same mouse.
Explain your answer.
2. Would the nucleotide composition of your original DNA sample be
different from the nucleotide composition of a tissue sample from your
gametes? Explain you answer.
3. Would the nucleotide composition of your liver tissue DNA sample be
different from the nucleotide composition of a tissue sample from the liver
of a deer? Explain your answer.
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Hand in the Procedure and Analysis Questions
2. Draw a linear stretch of double stranded DNA molecule 10
base pairs long, with a nucleotide sequence that corresponds to
the nucleotide composition of your sample.
Start by building the left side first; then build the
complementary right side. Use solid lines to show covalent
bonds and dotted lines to show hydrogen bonds. (see diagram
on the first page)
Make sure your purines, adenine and guanine, have a
double-ring structure. Make sure your pyrimidines, cytosine and
thymine, have a single-ring structure.
Label the 5' and 3' ends.
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Key Concept B: DNA Replication (p. 630-633)
B1. Semi-Conservative Replication of DNA p.630633
DNA Replication happens in the following three stages:
SEPARATING THE STRANDS
Voc abular y
Semi-Conservative Replication:
1. DNA helicase unzips the double helix by breaking the hydrogen
bonds between the complimentary bases in the two strands
BUILDING THE COMPLEMENTARY STRAND
Draw a model of Semi-Conservative Replication:
2. DNA polymerase III adds complementary nucleotides to the
growing strands, adenine pairs with thymine and cytosine pairs
with guanine, using the exposed strands of the parent DNA
molecule as a template. DNA polymerase can only
synthesize new DNA in a 5’ to 3’ direction
3. The leading strand is formed continuously
4. The lagging strand is formed in short fragments, starting from an
RNA primer.
5. DNA polymerase I cuts out the RNA primers and replaces them
with the appropriate DNA nucleotides.
6. DNA ligase joins the fragments
DNA REPAIR
7. Trailing DNA polymerase enzymes “check” the base pairs to
ensure that correct pairing has occurred.
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DNA Replication
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Key Concept C: Protein Synthesis (p. 636-642)
C1. Genes and the Genetic Code p.629-630 &
p.637-637
C2. The Nature of RNA & Amino Acids p.636-637
There are three different types of RNA involved in protein synthesis.
Voc abular y
What does RNA stand for:
Gene:
______________________________________________
List three ways in which RNA is different than DNA:
Cenral Dogma of Protein Synthesis (p.636):
The genetic code is much like a book, where the arrangement of
letters (in this case nucleotides) will result in different meanings
(in this case different amino acids)
1.
2.
3.
How many nucleotides code for one amino acid?
How many different types of amino acids are there?
In RNA, the nucleotide thymine is replaced by ________________.
Describe how the genetic code is….
a) redundant:
Types of RNA:
What does the “m” stand for in mRNA?
b) continuous:
What does the “r” stand for in rRNA?
What does the “t” stand for in tRNA?
c) universal:
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C3. Transcription p.637-638
Voc abular y
What does the word Transcription mean?
Where does mRNA transcription take place in the cell?
Steps in DNA Transcription
1. The two strands of a DNA molecule, sense and antisense,
separate along the length of a gene
2. The antisense strand forms the template for transcription; the
sense strand is transcribed
3. RNA polymerase binds at a site called the promoter region: this
determines where transcription starts.
4. RNA nucleotides form hydrogen bonds with the complementary
nucleotide sequence of the DNA strand, however the base
thymine is replaced with uracil.
5. The enzyme RNA polymerase will attach individual RNA
nucleotides together to extend the growing mRNA molecule.
6. When the RNA polymerase reaches the terminator sequence, it
detaches from the DNA and the newly formed mRNA strand is
released
7. The DNA double helix reforms
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C4. Translation
Steps in Translation:
On the series of diagrams to the right, identify the
following:
•
•
•
•
•
mRNA
rRNA (ribosome)
tRNA
A codon
An anti-codon
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C5. Control of Gene Expression
Indicate
As a zygote divides, groups of cells take on different shapes
and functions. This process is called ____________________
Muscle
Cell
Each different cell has all the genes, but different genes are
active in different kinds of cells.
A sophisticated regulatory system of control genes switches
protein synthesis genes on and off, responding to environmental
changes and shaping the differentiation of various cell lineages.
in the boxes below to show which genes you think would
be active in each of the cell types. Write switched "on"
or switched "off"
Pancreas
Cells
alpha
beta
cells
cells
Blood Cells
WBC
R BC
Genes for….
glycolysis
enzymes
Muscle
contraction
Proteins (actin
& myosin)
glucagon
insulin
hemoglobin
Specialized cells may retain all of their genetic potential. Because of this
ability, it is possible to switch on genes from a single specialized cell and
manipulate the cell to reactivate and recognize that it is a single zygote
cell. This zygote will then begin the embryological process, resulting in a
cloned organism.
Stem cells are undifferentiated cells that can be transformed into
specialized tissues. Stem cell research is attempting:
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Key Concept D: Mutations (p.644-645)
D1. Causes of Mutations p.644-645
Voc abular y
List three examples of physical mutagens:
1.
2.
3.
List three examples of chemical mutagens:
1.
2.
D2. Types of Mutations
Same-Sense Mutations: Mutations that do not affect the final gene
product. The mutated DNA sequence produces the same protein as the
original DNA sequence.
Level of Severity: _________________
Mis-Sense Mutations: Mutations change the DNA sequence, and the
resulting protein, but the protein is still functional in some capacity.
Level of Severity: _________________
Non-Sense Mutations: Mutation changes the DNA sequence and the
protein such that the protein no longer functions.
Level of Severity: _________________
3.
Mutations come in 3 main varieties:
Mutations generally result in a protein that does not function as
well or does not function at all. In some rare cases, mutations
can provide an advantage and be beneficial. These changes
may give that organism a competitive advantage.
Point Mutation: A change in the DNA sequence at one specific location.
These include:
• base substitutions
• addition and deletions of bases (resulting in a reading frame shift
unless they occur in multiples of three)
• tautomerism (incorrect base pairing)
Chromosome Mutation: Whole sections of chromosome are rearranged.
This often leads to promoters being placed before genes that control the
cell cycle. These types of mutations generally lead to cancer.
Chromosome Number Mutations: incorrect number of chromosomes
resulting from an error in spermatogenesis or oogenesis.
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Pr ac tice
Point Mutations. Using the following DNA sequence, write a
new DNA sequence that would result from each type of point
mutation. Show the corresponding polypeptide and indicate
whether you think it will be nonsense, missense, or samesense.
DNA:
Chromosome Mutations
AAT CGG CTC AAC GGT AAA
Polypeptide:
Substitution
New DNA Sequence:
Polypeptide:
Severity:
Addition
New DNA Sequence:
Polypeptide:
Severity:
Deletion
New DNA Sequence:
Polypeptide:
Severity:
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Chromosome Number Mutations
Voc abular y
Karyotope:
Identify the chromosome mutation for each of the following
syndromes:
Down syndrome:
Patau Syndrome:
Edward Syndrome:
Turner Syndrome:
Klinefelter Syndrome:
Jacobs Syndrome:
Triple X Syndrom (yes, this is a real disorder):
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Key Concept E: Genetic Technologies (p.648-651)
E1. Restriction Enzymes and Ligases p.648
Origin of Restriction Endonucleases
Restriction Enzymes: are like molecular scissors that can cut
double-stranded DNA at a specific base pair sequence.
Example: The restriction enzyme called EcoR1 cuts the DNA at
a specific recognition site: GAATTC . Each DNA strand is cut,
leaving overhanging ends called sticky ends.
Ligase: an enzyme that is used to join complementary DNA
fragments together.
Recombinant DNA . DNA molecule that includes genetic material
from different sources.
Restriction enzymes, such as endonucleases, have been isolated from
many bacteria.
Restriction enzymes are named according to the bacterial species from
which they were first isolated. There are now hundreds of restriction
enzymes used by genetic engineers.
Recognition Sites for Selected Restriction Enzymes
Enzyme
Source
EcoR1
BamH1
Escherichia coli
BAcillus
amyloliquefaciens
Haemophilus
aegyptius
Haemophilus
influenzae
Haemophilus
parainfluenzae
Haemophilus
parainfluenzae
Moraxella bovis
Norcardia otitdiscaviarum
Thermus aquaticus
Hae III
1.
2.
Hind III
Hpa1
Hpa II
Mbo 1
Not 1
3.
Taq 1
Recognition
Site
GAATTC
GGATCC
GGCC
AAGCTT
GTTAAC
CCGG
GATC
GCGGCC
GC
TCGA
4.
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Practice Question: A genetic engineer wants to use the
restriction enzyme BamH1 which cuts each DNA sequence after
its first guanine nucleotide.
a) Consult table on the previous page and write out the
recognition site for this enzyme:_________
b) Circle every recognition site on the DNA sequence below
that would be cut by BamH1.
AATGGGTACG CACAGTGGAT CCACGTAGTA TGCGATGCGT
AGTGTTTATG GAGAGAAGAA AACGCGTCGC CTTTTATCGA
TGCTGTACGG ATGCGGAAGT GGCGATGAGG ATCCATGCAA
TCGCGGCCGA TCGXGTAATA TATCGTGGCT GCGTTTATTA
TCGTGACTAG TAGCAGTATG CGATGTGACT GATGCTATGC
TGACTATGCT ATGTTTTTAT GCTGGATCCA GCGTAAGCAT
TTCGCTGCGT GGATCCCATA TCCTTATATG CATATATTCT
TATACGGATC GCGCACGTTT
This pattern is called a DNA fingerprint
DNA fingerprinting: a technique used to distinguish between
individuals of the same species using samples of their DNA
Example: DNA from a section of chromosome 4 of two different
individuals
c) State how many fragments of DNA were created by this
action.___________
E2. Gel electrophoresis and DNA fingerprinting
p.649-650
Gel Electrophoresis is a method that separates large molecules (
DNA or proteins) on the basis of mass and electric charge. text
p. 649-650
To prepare DNA for gel electrophoresis a DNA sample is cut
up into fragments with
______________________________________.
What would the DNA fingerprint look like of each individual?
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E3. PCR
PCR is a technique for amplifying a DNA sequence by repeated
cycles of strand separation and replication
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Key Concept F: Biotechnology products
(p. 654-658)
Steps in Cloning hGH , using a bacterial plasmid
Voc abular y
genetic engineering:
transgenic organisms:
F1. Transgenic Bacteria / Gene Cloning
Transformation of bacteria: Bacteria are the most common
organisms that are transformed by genetic engineers.
Transgenic bacteria may be used to study gene expression or
gene function, to create and maintain a stock of particular DNA
fragment, or to synthesize a useful gene product.
For example, transgenic bacteria have been engineered to
produce human insulin for diabetics and human growth
hormone, used in treatment of pituitary dwarfism.
The use of recombinant DNA hGH raises ethical questions:
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F2. Transgenic Plants & Animals
Notes
Transgenic plants:
There are organizations that have opposed the use of transgenic
organisms. Some risks cited by these groups:
-Environmental threats
-Health effects
-Social and economic issues
Use text p. 657 to expand upon each of the above risks
Summarize the role of golden rice as a transgenic plant.
Explain how this transgenic plant helps achieves a
social, economic or environmental goal.
Transgenic animals:
Give an example of a transgenic animal that helps
achieve a social, economic, or environmental goal.
Explain how the transgenic animal achieves this.
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Key Concept G: Diagnosis and treatment of genetic disorders
G1. Genetic Counseling: Prior to having children, parents
can seek out a genetic councilor to inform them of the risks of
having a child with a genetic disorder. The councilor takes a full
family history and based on genetic inheritance patterns can
predict certain probabilities. The parents can then decide
whether or not it is worth the risk. Genetic counseling is not
common and is generally only done when there is a significant
family history of genetic disorders and parents are concerned
about their own children.
G2. Prenatal Diagnosis
Voc abular y
(p. 658-661)
G3. Genetic Screening
Genetic material from fetal tissue, a child or an adult can be screened for
genetic markers.
genetic markers : a characteristic that provides information about the
genotype of the individual
DNA probe:
How is a DNA probe used to screen for genetic conditions?
Explain how the following procedures can contribute to
the diagnosis of genetic conditions.
ultrasound:
G4. Treating human disorders
Voc abular y
amniocentesis:
gene therapy:
chorionic villi sampling:
DNA vector:
Differentiate between somatic gene therapy and germ-line gene
therapy:
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Example of gene therapy
Issues Related to Gene Therapy
Technological issues:
How can scientists be sure that the gene’s insertion does not harm some
other necessary cell function?
Societal issues:
Should gene therapy be reserved for treating serious diseases or should
we explore the potential use for enhancing athletic ability, physical
appearance, or even intelligence?
Should we try to eliminate genetic defects in our children and their
descendants? Should we interfere with evolution in this way? From a
biological perspective, the elimination of unwanted genes from the gene
pool could backfire. Genetic variety is a necessary ingredient for the
survival of a species as environmental conditions change with time.
Genes that are damaging under some conditions may be advantageous
under others. (one example is the sickle-cell gene) Are we willing to risk
making genetic changes that could be detrimental to our species in the
future?
Should we use gene therapy on those who can afford it, or should we
have unlimited access by all , thereby increasing taxes to cover health
costs? The procedures now being tested are expensive and require
expertise and equipment found only in major medical centers.
Should we use gene therapy to such an extent that we support the
eugenics movement? Largely because of the events of Nazi Germany,
our society rejects the notion of eugenics— the effort to control the
genetic makeup of human populations. The possibility of gene therapy
raises fears in this regard.
Ethical issues:
Provide two ethical issues associated with genetic screening and
gene therapy. text p. 661
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