Question 1

Which enzyme is primarily responsible for relieving supercoiling ahead of the replication fork during DNA replication in E. coli?

Accepted Answer

DNA gyrase

Question 2

During DNA replication, what is the main function of single-stranded DNA binding proteins (SSB)?

Accepted Answer

To stabilize and keep the DNA strands separated and accessible for replication

Question 3

In the trombone model of DNA replication, what is the purpose of the lagging strand forming a loop?

Accepted Answer

To allow simultaneous synthesis of both leading and lagging strands by the replisome

Question 4

Which protein complex in the replisome is responsible for keeping DNA polymerase attached to the DNA during replication?

Accepted Answer

Sliding clamp

Question 5

What is the sequence most commonly found in human telomeres?

Accepted Answer

$	ext{TTAGGG}$

Question 6

A patient with Werner syndrome exhibits premature aging. What is the molecular basis for this condition?

Accepted Answer

Lack of telomere cap protein (WRN)

Question 7

Which DNA repair mechanism is most likely to correct a thymine dimer caused by UV radiation in the presence of visible light?

Accepted Answer

Photoactive (light-dependent) repair

Question 8

What is the main difference between nonhomologous end-joining (NHEJ) and synthesis-dependent strand annealing (SDSA) in double-strand break repair?

Accepted Answer

NHEJ is error-prone and can result in loss of nucleotides, while SDSA uses a homologous template and is more accurate

Question 9

Which of the following is a common cause of spontaneous mutations during DNA replication?

Accepted Answer

Tautomeric shifts in nitrogenous bases

Question 10

A cell line is able to divide indefinitely in culture. Which enzyme is most likely active in these cells?

Accepted Answer

Telomerase

Question 11

Which repair pathway is responsible for removing and replacing a single damaged base, such as uracil formed by cytosine deamination?

Accepted Answer

Base excision repair

Question 12

What is the role of DNA methylation in bacterial mismatch repair?

Accepted Answer

It allows the repair system to distinguish the template strand from the newly synthesized strand

Question 13

Which type of mutagenic agent is most likely to cause frameshift mutations by inserting itself between DNA bases?

Accepted Answer

Intercalating agents

Question 14

A scientist exposes cells to ethidium bromide. What type of DNA damage is most likely to occur?

Accepted Answer

Intercalation between DNA bases, causing distortion of the double helix

Question 15

Which enzyme is responsible for directly repairing pyrimidine dimers in a light-dependent manner?

Accepted Answer

Photolyase

Question 16

What is the consequence of repeated rounds of DNA replication in somatic cells lacking telomerase?

Accepted Answer

Progressive shortening of telomeres leading to cell senescence and apoptosis

Question 17

Which repair pathway is most versatile and can correct a wide variety of DNA lesions, including those that distort the DNA helix?

Accepted Answer

Nucleotide excision repair (NER)

Question 18

What is the role of RecA protein in the SOS response of E. coli?

Accepted Answer

It facilitates the expression of bypass polymerases to allow replication past DNA damage

Question 19

Which of the following best describes the function of chromatin remodeling proteins during DNA replication in eukaryotes?

Accepted Answer

They loosen nucleosome packing to allow replication machinery access to DNA

Question 20

A mutation causes the loss of function of the clamp loader protein in the replisome. What is the most likely consequence?

Accepted Answer

DNA polymerase will frequently dissociate from the DNA, reducing replication efficiency

DNA Replication, Telomeres, Mutations, and DNA Repair Mechanisms

Study Guide - Practice Questions