Biology 30 Review of Moleular Genetics
Name:
________________________________
Multiple Choice
Identify the choice that best completes the statement or answers the question.
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1. A molecule of DNA has a sequence of bases that read ATTCAGTAC. The base sequence of the
complimentary strand is
A. ATTCAGTAC
B. TAACTGATC
C. TAAGTCATG
D. CATGACTTA
Figure 20.1 DNA Strand
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2. Use the Figure 20.1 to answer the following question.
The molecule being copied from the DNA strand represents
A. complimentary DNA
B. rRNA
C. tRNA
D. mRNA
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3. Use the Figure 20.1 to answer the following question.
The diagram illustrates the process of
A. replication
B. transcription
C. translation
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D. duplication
4. Which of the following statements related to the roles of various molecules during the process
of protein synthesis are correct.
A. The tRNA molecule is the site where the DNA code is translated.
B. The mRNA is a copy of a section of the DNA code.
C. The tRNA carries the DNA message from the nucleus to the ribosome.
D. The rRNA is the molecule which transports the amino acids to the ribosome.
Figure 20.2
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5. Use Figure 20.2 to answer the following question.
The structures labeled X, Y and Z respectively represent
A. mRNA, codon, ribosome
B. mRNA, protein molecule, tRNA
C. mRNA, tRNA, ribosome
D. DNA, codon, mRNA
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6. Use Figure 20.2 to answer the following question.
The diagram illustrates the process of
A. transcription
B. translation
C. replication
D. duplication
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7. Use Figure 20.2 to answer the following question.
The function of the molecule labeled Y is to
A. transport amino acids to the ribosome
B. transport the DNA code to the ribosome
C. identify mutations in the DNA sequence
D. carry out the process of transcription
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8. In an experiment, a group of rabbits were given an injection of a radioactive isotope. Another
group was exposed to the same dosage of radiation, but over the period of a few weeks.
Significantly lower mutations were found in the group exposed to radiation for a longer period
of time. This is due to the fact that
A. a repair mechanism for mutations in the DNA is at work.
B. it is the length of time and not the amount of radiation that is significant.
C. small doses of radiation are not harmful.
D. small doses of radiation does not effect bases in DNA.
Scenario 20.1 Mustard Gas
Mustard gas was used during the First World War causing the painful deaths of many soldiers.
The chemical in mustard gas causes mutations to occur in the DNA lining the respiratory system
Original sequence of nucleotides in a DNA molecule.
CAT CAG TTC AGC
Sequence of nucleotides after exposure to mustard gas.
CAT CAG CTC AGC
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9. Use Scenario 20.1 to answer the following question.
The type of gene mutation shown in the above example is
A. reversion
B. substitution
C. deletion
D. addition
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10. Use Scenario 20.1 to answer the following question.
In the mutated DNA sequence, the amino acid that is switched in the sequence is
A. leucine to valine
B. lysine to glutamic acid
C. lysine to valine
D. leucine to glutamic acid
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11. Suppose that a mutation occurred where a base pair in the DNA molecule was added. This
would cause the codons to be shifted over by one base molecule. This would result in
A. the addition of an amino acid in the protein synthesized.
B. a change in the reading frame of the entire chromosome.
C. a change in the reading frame for that gene.
D. deletion of an amino acid in the protein synthesized.
Example 20.1 Portion of Insulin Protein
Phenylalanine - Valine - Asparagine - Glutamine - Histidine
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12. Use Example 20.1 to answer the following question.
The strand of DNA that would code for this portion of insulin is
A. CAC GAG AAC GTA TTC
B. TTC GTA AAC GAG CAC
C. AAG CAA TTA GTT GTA
D. AAA CAA TTC CAC CTA
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13. Some of the substances that are required for protein synthesis to occur are
A. salts and amino acids
B. enzymes and amino acids
C. enzymes and salts
D. fats and amino acids
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14. A codon can be described as
A. the code for one amino acid
B. a nucleotide with 3 bases
C. a code for a protein
D. a nucleotide
Scenario 20.3 Huntingtons Disease
In an individual with Huntingtons disease, part of the coding strand of DNA that has been
deleted has the following base sequence.
ATT CAG GAT TTT ACG
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15. Use Scenario 20.3 to answer the following question
.
The second amino acid coded for by this short segment of DNA is
A. glutamine
B. aspartic acid
C. leucine
D. valine
Scenario 20.2 Breast Milk
A study published in the journal Pediatrics shows that infants who are breast fed have a much
lower risk of developing diarrhea when compared to infants who are fed formula. A different
study reports that while many infants contain bacteria in their digestive system that would
cause diarrhea in adults, breast fed infants do not become ill. A bacterium specific to the human
digestive system produces a toxin which irritates the lining of the digestive system resulting in
diarrhea. Breast milk contains a protein which binds to the toxin produced by the bacteria
resulting in it being ineffective.
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16. Use Scenario 20.2 to answer the following question.
The protein found in breast milk is produced when
A. DNA is replicated
B. DNA is translated
C. mRNA is translated
D. mRNA is replicated
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17. Use Scenario 20.2 to answer the following question.
The toxin produced by the bacteria that is responsible for the development of diarrhea is
produced by a section of DNA that has the code CCT TAT CAG. The sequence of amino acids
produced by this sequence is
A. glycine - isoleucine - aspartic acid
B. glycine - isoleucine - valine
C. glycine - tyrosine - valine
D. glycine - tyrosine - isoleucine
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18. Use Scenario 20.2 to answer the following question.
The number of codons shown by the section of DNA coding for the protein found in breast milk
that contains the base sequence ACTTACCAG is
A. 4
B. 9
C. 3
D. 1
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19. A code of 5 amino acids contains a DNA sequence of
A. 5 bases
B. 10 bases
C. 15 bases
D. 25 bases
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20. In protein synthesis, tRNA
A. initiates the transcription process.
B. collects and transfers amino acids.
C. ensures that the correct codons are translated into amino acids.
D. acts as the site for the synthesis of an amino acid chain.
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21. Which of the following structures is composed of a specific sequence of amino acids?
A. DNA
B. RNA
C. nucleotide
D. polypeptide chain
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22. An anticodon consists of three
A. amino acids attached to rRNA
B. DNA nitrogen bases
C. mRNA nitrogen bases
D. tRNA nitrogen bases
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23. HIV is a retrovirus which is a class of viruses that has its traits encoded by RNA instead of DNA.
Retroviruses utilize an enzyme called reverse transcriptase which acts by invading the host cell’s
DNA. The function of reverse transcriptase is to
A. prevent DNA replication
B. prevent protein synthesis
C. transcribe RNA into DNA
D. transcribe DNA into RNA
Figure 20.3 DNA Replication
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24. Use Figure 20.3 to answer the following question.
The process shown by the diagram occurs in
A. cell division
B. transcription
C. translation
D. recombination
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25. Initiators and terminators (start and stop codons) are important to protein synthesis because
they specify
A. where the mRNA chain should start and finish.
B. which amino acids should be included in the protein.
C. where the amino acids should be added at the ribosome.
D. when the DNA replication begins and ends.
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26. Since the first nucleotides cannot be linked in a newly synthesized strand in DNA replication,
__________ is required.
A. an RNA primer
B. a DNA primer
C. DNA polymerase
D. ligase
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27. Unlike DNA, an RNA molecule
A. contains uracil.
B. contains deoxyribose sugar.
C. moves from the cytoplasm to the nucleus.
D. is double stranded.
Figure 20.4 DNA Replication II
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30. Use Figure 20.4 to answer the following question.
The diagram illustrates the process of
A. replication
B. translation
C. transcription
D. duplication
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31. The following statements are related to the various roles molecules play during the process of
protein synthesis.
1. The rRNA molecule carries amino acids to the ribosome.
2. The tRNA is where the code is translated.
3. The mRNA is a copy of the DNA molecule.
4. The mRNA carries the message from the nucleus to the ribosomes.
Which of the statements are correct?
A. 1 and 2
B. 1 and 3
C. 2 and 3
D. 3 and 4
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32. The following statements represent the roles of various molecules during the process of protein
synthesis.
1. Amino acids are linked to form a polypeptide.
2. The genetic code of the DNA is transcribed.
3. Matching of the anticodon of the tRNA with the codon of the RNA.
4. The DNA molecule unwinds and unzips.
Which of the following represents the sequence of events that occurs as a protein is
synthesized?
A. 2,3,1,4
B. 4,2,3,1
C. 4,3,1,2
D. 4,3,2,1
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33. A student was asked to build a molecule of mRNA codon from the DNA codon ATT. The student
was given the following list of substances to work with for their model.
1. thymine
2. ribose sugar
3. deoxyribose sugar
4. uracil
5. phosphate
6. adenine
To form the nucleotides of the RNA codon, the molecule must include the substances numbered
A. 1,2,5,6
B. 1,3,5,6
C. 2,4,5,6
D. 3,4,5,6
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34. Which of the following are enzymes involved in posttranscriptional modification?
A. RNA polymerase and spliceosomes
B. RNA polymerase and poly-A polymerase
C. poly-A polymerase and spliceosomes
D. RNA polymerase, poly-A polymerase and spliceosomes
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35. What does an operon typically consist of?
A. an operator, a promoter, and a cluster of genes
B. a cluster of genes
C. a promoter and a cluster of genes
D. an operator and a cluster of genes
Completion
Complete each statement.
1. The nucleotides of a DNA molecule and an RNA molecule differ as DNA contains thymine and
RNA contains ______________________.
2. The process of transcription involves converting the DNA code into a molecule of
____________________.
3. Mutations are changes in the DNA that result in the incorrect sequence of
_______________________ in the development of a protein.
4. When a molecule of DNA is replicated, the base sequences ACAATG is copied to make a
complimentary strand with the sequence ___________________.
5. The start codon found at the beginning of every mRNA molecule is ___________________.
6. Transcription occurs through the processes of initiation, elongation and
____________________.
7. The DNA sequence ACC TAG codes for the amino acids ____________________ and
____________________.
8. The DNA of eukaryotic organisms contains coding regions called ____________________ and
non coding regions called ____________________.
9. The role of bringing amino acids to the ribosome during the process of translation belongs to
the _________________________.
10. A mutation that causes the reading frame of codons to change resulting in the incorporation of
different amino acids into the sequence is called a ____________________ mutation.
Matching
Match each item with the correct statement below.
A. mRNA
E.
B. tRNA
F.
C. amino acid
G.
D. RNA Polymerase
H.
codon
transcription
translation
mutation
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1. Molecules that are linked together to form a polypeptide.
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2. DNA copy used to create an amino acid sequence.
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3. Puts together the appropriate nucleotides to build an mRNA molecule.
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4. Moves amino acids from the cytoplasm to the ribosome to build the protein.
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5. Errors made in the DNA sequence that are inherited.
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6. A triplet of nucleotides that codes for an amino acid.
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7. The conversion of a DNA sequence into an mRNA sequence.
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8. The conversion of an mRNA sequence into an amino acid sequence.
Short Answer
1. Fill in the table that gives the base sequence of a section of a DNA molecule. Assume that the
code is being read from left to right, and that the upper strand of the DNA code is being
transcribed.
C
DNA
C
T
U
A
Trp
G
A
mRNA
tRNA
amino acids
2. What is the function of each of the following in protein synthesis: tRNA, mRNA, rRNA?
3. Differentiate between transcription and translation.
4. The following polypeptide sequence has been obtained from a protein found in eukaryotic cells.
met-gly-pro-val-arg
a) List a possible mRNA sequence that may have coded for this protein.
b) Explain why more than 1 sequence may be possible.
c) How can variability in mRNA sequence due to mutation result in the same sequence of amino
acids?
5. While DNA replication and transcription are similar process, there are significant differences
between the two. Provide two differences between the processes.
6. Poisonous mushrooms contain a substance called alpha-amanitin. Trace amounts of this
substance stop body cells from synthesizing mRNA. Explain why eating these mushrooms could
be fatal.
7. Children suffering from thalassemia are homozygous for a gene that is involved in the
production of hemoglobin. The mutated gene changes the CAG codon into UAG in the mRNA.
Explain how this will affect the protein produced.
8. The mapping of the human genome has the potential to be one of the most beneficial
discoveries in science. How will the mapping of human chromosomes be beneficial in the
treatment of genetic diseases?
10. The following sequence of bases is found in a small portion of DNA
ATTACGGACT
a) What is the base sequence in the replicated strand of this molecule?
b) What molecules are found in the backbone of each strand?
11. Explain why the manner in which DNA is replicated is called semiconservative replication.
14. Identify the controversial side of the human genome project.