Uark Genetics Exam 2 Questions and
Answers
1. A class of mutations that results in multiple contiguous amino acid
changes in proteins is likely to be the following: - -d. Frameshift
- 2. Mutations that reduce the function encoded by the wildtype allele are
known as _______, while mutations that eliminate all function are known as
______. - -b. Hypomorphic mutations; null mutations
- 3. Deamination of cytosine: - -c. Can be repaired by base-excision repair
- 4. Neutral mutations: - -Do not alter the product of a gene
Occur frequently in the noncoding regions of the genome
Can be used to estimate mutation rates
Are expected to accumulate over time
*all of these are correct
- 5. Genes within an operon: - -Tend to be regulated by a common
regulatory mechanism.
Are generally involved in the same biochemical pathway.
Are expressed as a polycistronic RNA.
*all are correct
- 6. The lac repressor... - -Binds to the operator in the Lac operon
Binds lactose
- 7. Which of the following would you expect to find in an inducible system? -
-a. A repressor protein, which is bound to DNA in absence of any other factor.
- 8. DNA sites bound by regulatory transcription factors: - -b. Are cis acting
elements.
- 9. The zinc-finger motif functions to - -b. Anchor transcriptional activator
proteins to enhancer sequences
- Which of the following point mutations would be most likely to affect
protein function?
A) TAA to TGA
B) CAA to TAA
C) AGG to AGA
, D) CTT to CTC
E) All of these are likely to affect protein function. - -B) CAA to TAA
- Which of these describes a similarity between the lac and ara operons?
A) Expression of structural genes does not occur at high glucose
concentrations.
B) lacI and araI both encode transacting factors.
C) Binding of a regulatory protein is prevented in the presence of an inducer.
D) All of these are similarities.
E) Noneofthesearesimilarities. - -A) Expression of structural genes does not
occur at high glucose concentrations
- Assume that in the organism under study the DNA polymerase has an error
rate of 1 mistake in every 10^6 bases copied. However, the overall mutation
rate is much lower. This is most likely because:
A)the polymerase is more careful in replicating regions where genes exist.
B)repair mechanisms correct errors made by the polymerase.
C)not all mutations can be detected easily.
D)the DNA polymerase has no proofreading function. mutations do not occur
if mutagens are not present. - -repair mechanisms correct errors made by
the polymerase.
- The quaternary structure of proteins is represented by the __________.
A) amino acid sequence
B) alpha helix
C) arrangement of subunits
D) beta-pleated sheet
E) three-dimensional conformation - -C) arrangement of subunits
- In Neurospora, a mutation was induced that causes the loss of function of
an enzyme essential to the biosynthesis of the vitamin pyridoxine. On which
medium will such organisms NOT grow?
A) minimal
B) minimal+allvitamins
C) minimal + valine + pyridoxine D) complete
E) minimal+pyridoxine - -A) minimal
- A mutation arose in the guinea pig genome through the course of evolution
that affects the ability to produce ascorbic acid, or vitamin C. The mutation
maps to a gene encoding an enzyme in the biosynthetic pathway that
Answers
1. A class of mutations that results in multiple contiguous amino acid
changes in proteins is likely to be the following: - -d. Frameshift
- 2. Mutations that reduce the function encoded by the wildtype allele are
known as _______, while mutations that eliminate all function are known as
______. - -b. Hypomorphic mutations; null mutations
- 3. Deamination of cytosine: - -c. Can be repaired by base-excision repair
- 4. Neutral mutations: - -Do not alter the product of a gene
Occur frequently in the noncoding regions of the genome
Can be used to estimate mutation rates
Are expected to accumulate over time
*all of these are correct
- 5. Genes within an operon: - -Tend to be regulated by a common
regulatory mechanism.
Are generally involved in the same biochemical pathway.
Are expressed as a polycistronic RNA.
*all are correct
- 6. The lac repressor... - -Binds to the operator in the Lac operon
Binds lactose
- 7. Which of the following would you expect to find in an inducible system? -
-a. A repressor protein, which is bound to DNA in absence of any other factor.
- 8. DNA sites bound by regulatory transcription factors: - -b. Are cis acting
elements.
- 9. The zinc-finger motif functions to - -b. Anchor transcriptional activator
proteins to enhancer sequences
- Which of the following point mutations would be most likely to affect
protein function?
A) TAA to TGA
B) CAA to TAA
C) AGG to AGA
, D) CTT to CTC
E) All of these are likely to affect protein function. - -B) CAA to TAA
- Which of these describes a similarity between the lac and ara operons?
A) Expression of structural genes does not occur at high glucose
concentrations.
B) lacI and araI both encode transacting factors.
C) Binding of a regulatory protein is prevented in the presence of an inducer.
D) All of these are similarities.
E) Noneofthesearesimilarities. - -A) Expression of structural genes does not
occur at high glucose concentrations
- Assume that in the organism under study the DNA polymerase has an error
rate of 1 mistake in every 10^6 bases copied. However, the overall mutation
rate is much lower. This is most likely because:
A)the polymerase is more careful in replicating regions where genes exist.
B)repair mechanisms correct errors made by the polymerase.
C)not all mutations can be detected easily.
D)the DNA polymerase has no proofreading function. mutations do not occur
if mutagens are not present. - -repair mechanisms correct errors made by
the polymerase.
- The quaternary structure of proteins is represented by the __________.
A) amino acid sequence
B) alpha helix
C) arrangement of subunits
D) beta-pleated sheet
E) three-dimensional conformation - -C) arrangement of subunits
- In Neurospora, a mutation was induced that causes the loss of function of
an enzyme essential to the biosynthesis of the vitamin pyridoxine. On which
medium will such organisms NOT grow?
A) minimal
B) minimal+allvitamins
C) minimal + valine + pyridoxine D) complete
E) minimal+pyridoxine - -A) minimal
- A mutation arose in the guinea pig genome through the course of evolution
that affects the ability to produce ascorbic acid, or vitamin C. The mutation
maps to a gene encoding an enzyme in the biosynthetic pathway that
