Question 1

Double-stranded break repair mechanisms
A)are error prone.
B)may join nonhomologous ends of DNA together.
C)are part of the SOS repair system.
D)may use homologous DNA to repair the damage.
E)are error prone and may join nonhomologous ends of DNA together or use homologous DNA to repair the damage.

Accepted Answer

Double-stranded break repair mechanisms can be error-prone and have the ability to join nonhomologous ends of DNA together, which can lead to mutations or chromosomal rearrangements. They can also use homologous DNA sequences to accurately repair the damage, which is a less error-prone process. This encompasses both non-homologous end joining (NHEJ) and homologous recombination (HR) repair mechanisms.

Question 2

Cells that are very sensitive to UV radiation most likely have a defect in the
A)base excision repair pathway.
B)SOS repair pathway.
C)nonhomologous end-joining pathway.
D)nucleotide excision repair pathway.
E)synthesis-dependent strand annealing pathway.

Accepted Answer

Cells that are very sensitive to UV radiation most likely have a defect in the nucleotide excision repair pathway. This pathway is specifically responsible for repairing bulky lesions such as thymine dimers, which are primarily caused by UV radiation.

Question 3

Composite transposons are composed of
A)the transposase gene flanked by inverted repeat sequences.
B)a mobile gene flanked by inverted repeat sequences.
C)the transposase gene only.
D)several genes,such as antibiotic resistance genes,flanked by transposase genes.
E)several genes,including transposase,flanked by inverted repeat sequences.

Accepted Answer

Composite transposons consist of several genes, including transposase, flanked by inverted repeat sequences, which facilitate their movement within the genome.

Question 4

In hereditary nonpolyposis colon cancer,mutations in MutS and MutH proteins result in the accumulation of mutations caused by
A)mismatched base pairs.
B)structurally damaged bases.
C)double-stranded DNA breaks.
D)thymine dimers.
E)DNA recombination.

Accepted Answer

Mismatch repair proteins, such as MutS and MutH, are involved in correcting errors that occur during DNA replication, such as mismatched base pairs. In hereditary nonpolyposis colon cancer (HNPCC), mutations in these proteins lead to an accumulation of replication errors, contributing to cancer development.

Question 5

Linear chromosomes have multiple sites of DNA replication known as ________.

Accepted Answer

The answer of Linear chromosomes have multiple sites of DNA...

Question 6

A way of making multiple copies of a segment of DNA from a single template (without culturing cells)is known as ________.

Accepted Answer

The answer of A way of making multiple copies of...

Question 7

Which of the following DNA repair mechanisms is most prone to error?
A)mismatch repair
B)base excision repair
C)SOS repair
D)nucleotide excision repair
E)All DNA repair systems are equally prone to error.

Accepted Answer

SOS repair is most prone to error because it is an emergency repair mechanism activated in bacteria under severe DNA damage conditions. It allows DNA replication to proceed past lesions that would normally stall the replication fork, but it does so with lower fidelity, leading to an increased rate of mutations.

Question 8

Small pieces of DNA synthesized on the lagging strand are called ________.

Accepted Answer

The answer of Small pieces of DNA synthesized on the...

Question 9

Base excision repair is used to
A)correct base mismatches in newly synthesize DNA.
B)fix double-strand DNA breaks.
C)remove intercalating agents.
D)remove modified or depurinated bases.
E)remove intercalating agents and modified or depurinated bases.

Accepted Answer

Base excision repair is specifically designed to remove modified or depurinated bases from DNA, correcting small, non-helix-distorting base lesions.

Question 10

It has been observed that when plants are subjected to extreme physical stress such as drought or high salinity,the transcription and activity of transposase genes increases.Increased transposase activity may
A)increase the rate of mutation under stressful conditions.
B)aid in repairing DNA damage caused by stressful conditions.
C)halt DNA replication and cell division.
D)increase homologous recombination and genetic diversity.
E)explain why some plants can't withstand drought conditions.

Accepted Answer

Increased transposase activity can lead to higher rates of transposition, which can cause mutations by inserting transposable elements into new genomic locations, potentially increasing genetic variability and adaptability under stress.

Question 11

Nonhomologous end joining is used to
A)correct base mismatches in newly synthesized DNA.
B)fix double-strand DNA breaks.
C)avoid deletion or insertion of bases.
D)remove modified or depurinated bases.
E)avoid deletion or insertion of bases and remove modified or depurinated bases.

Accepted Answer

Nonhomologous end joining (NHEJ) is a pathway that repairs double-strand breaks in DNA. This process involves directly ligating the two ends of the DNA break without the need for a homologous template, which is different from homologous recombination repair that requires a homologous sequence to guide the repair.

Question 12

A 40-year-old patient has been diagnosed with cancer.Sequencing of cancer cell genomes reveals a high frequency of G/C to A/T base pairs conversion.The DNA repair system that is most likely deficient in this patient is the
A)base excision repair pathway.
B)SOS repair pathway.
C)nonhomologous end-joining pathway.
D)nucleotide excision repair pathway.
E)synthesis-dependent strand annealing pathway.

Accepted Answer

The base excision repair pathway is responsible for correcting small base lesions, such as G/C to A/T base pair conversions, by removing and replacing the incorrect bases. This pathway is crucial for fixing mutations that arise from deamination, oxidation, and other processes that alter the structure of individual nucleotides.

Question 13

Homologous recombination may result in gene conversion when used to fix double-stranded DNA breaks because
A)sister chromatids are always identical.
B)homologous recombination is prone to errors,potentially causing permanent genetic mutations.
C)strand invasion may introduce new genes onto the damaged chromosome.
D)homologous chromosomes may carry different alleles of the same gene.
E)the Holliday junction may migrate,resulting in loss of genetic material.

Accepted Answer

Homologous recombination involves the exchange of genetic material between homologous chromosomes, which can carry different alleles of the same gene. When repairing double-stranded DNA breaks, this process can lead to gene conversion if the sequence from one chromosome is used as a template to repair the other, potentially replacing one allele with another.

Question 14

The protein(s)that facilitate the unfolding of chromatin fibers ahead of the replication fork is (are)
A)helicase.
B)scaffold proteins.
C)chromatin remodeling proteins.
D)replisomal proteins.
E)helicase and scaffold proteins.

Accepted Answer

Chromatin remodeling proteins are responsible for modifying the structure of chromatin, allowing it to unfold or become more accessible for processes such as replication. This is essential for the replication machinery to access the DNA strands.

Question 15

Which of the following is involved in proofreading during DNA replication?
A)5' to 3' exonuclease activity of DNA polymerase
B)3' to 5' exonuclease activity of DNA polymerase
C)5' to 3' endonuclease activity of DNA polymerase
D)3' to 5' endonuclease activity of DNA polymerase
E)RNA polymerase

Accepted Answer

The 3' to 5' exonuclease activity of DNA polymerase is responsible for proofreading during DNA replication. This activity allows the enzyme to remove incorrectly paired nucleotides, ensuring the accuracy of the DNA copy.

Question 16

Multiple sites of DNA replication along eukaryotic chromosomes are known as
A)replicons.
B)multireplication forks.
C)helicase loaders.
D)ARS elements.
E)None of these answers are correct.

Accepted Answer

Replicons are the units of the genome in which DNA is replicated. In eukaryotic chromosomes, multiple sites of DNA replication, known as origins of replication, are part of larger replicons. Each replicon contains an origin where replication begins, indicating multiple origins along the chromosome for efficient replication.

Question 17

Transposase is
A)required to resolve a Holliday junction.
B)involved in the movement of mobile genetic elements in prokaryotic and eukaryotic genomes.
C)found only in prokaryotic transposons.
D)required for synthesis-dependent strand annealing to repair double-stranded DNA breaks.
E)necessary for replicative transposition but not conservative transposition.

Accepted Answer

Transposase is an enzyme that facilitates the movement of transposable elements or "jumping genes" across different positions within the genome of both prokaryotic and eukaryotic organisms, thus playing a crucial role in genome rearrangement and evolution.

Question 18

Which of the following proteins is observed exclusively in association with eukaryotic DNA replication?
A)DNA polymerase I
B)DNA gyrase
C)single-strand binding proteins
D)DNA ligase
E)telomerase

Accepted Answer

Telomerase is unique to eukaryotic cells and is specifically involved in the replication of the ends of linear chromosomes, a feature not present in prokaryotic organisms.

Question 19

The type of DNA repair that fixes mistakes in nucleotide incorporation after DNA replication is known as ________ repair.

Accepted Answer

The answer of The type of DNA repair that fixes...

Question 20

Which of the following eukaryotic DNA polymerases replicates mitochondrial DNA?
A)alpha
B)beta
C)delta
D)epsilon
E)gamma

Accepted Answer

Eukaryotic mitochondrial DNA is replicated by DNA polymerase gamma, not by the polymerases involved in nuclear DNA replication (alpha, beta, delta, epsilon).

Quiz 17: DNA Replication, repair, and Recombination

Double-stranded break repair mechanisms

Cells that are very sensitive to UV radiation most likely have a defect in the

Composite transposons are composed of

In hereditary nonpolyposis colon cancer,mutations in MutS and MutH proteins result in the accumulation of mutations caused by

Linear chromosomes have multiple sites of DNA replication known as ________.

A way of making multiple copies of a segment of DNA from a single template (without culturing cells)is known as ________.

Which of the following DNA repair mechanisms is most prone to error?

Small pieces of DNA synthesized on the lagging strand are called ________.

Base excision repair is used to

It has been observed that when plants are subjected to extreme physical stress such as drought or high salinity,the transcription and activity of transposase genes increases.Increased transposase activity may

Nonhomologous end joining is used to

A 40-year-old patient has been diagnosed with cancer.Sequencing of cancer cell genomes reveals a high frequency of G/C to A/T base pairs conversion.The DNA repair system that is most likely deficient in this patient is the

Homologous recombination may result in gene conversion when used to fix double-stranded DNA breaks because

The protein(s) that facilitate the unfolding of chromatin fibers ahead of the replication fork is (are)

Which of the following is involved in proofreading during DNA replication?

Multiple sites of DNA replication along eukaryotic chromosomes are known as

Transposase is

Which of the following proteins is observed exclusively in association with eukaryotic DNA replication?

The type of DNA repair that fixes mistakes in nucleotide incorporation after DNA replication is known as ________ repair.

Which of the following eukaryotic DNA polymerases replicates mitochondrial DNA?