Question 1

Which of the following statements best describes the semi-conservative nature of DNA replication?

Accepted Answer

Each newly synthesized DNA molecule consists of one old strand and one new strand.

Question 2

During DNA replication, which direction is the new DNA strand synthesized?

Accepted Answer

From 5' to 3'

Question 3

Arthur Kornberg’s experiments in 1956 demonstrated that DNA polymerase requires which of the following to synthesize DNA?

Accepted Answer

A DNA template

Question 4

Which enzyme is responsible for joining Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

DNA ligase

Question 5

A mutation that changes a codon but does not alter the amino acid sequence of the protein is called:

Accepted Answer

Synonymous (silent) mutation

Question 6

Which of the following best explains why DNA synthesis on the lagging strand is discontinuous?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, so the lagging strand is made in short fragments.

Question 7

Which repair mechanism is primarily responsible for correcting pyrimidine dimers caused by UV light?

Accepted Answer

Nucleotide excision repair

Question 8

A frameshift mutation is most likely to result from which of the following events?

Accepted Answer

Addition or deletion of a nucleotide

Question 9

In E. coli, how does the mismatch repair system distinguish the newly synthesized DNA strand from the template strand?

Accepted Answer

By delayed methylation of the new strand at GATC sequences

Question 10

Which of the following is the correct sequence of events in base excision repair?

Accepted Answer

DNA glycosylase removes the damaged base, AP endonuclease cuts the backbone, DNA polymerase fills the gap, DNA ligase seals the nick

Question 11

Which of the following best describes a missense mutation?

Accepted Answer

A mutation that changes one amino acid in the protein sequence

Question 12

If a DNA sequence undergoes deamination of cytosine, what base is produced?

Accepted Answer

Uracil

Question 13

Which enzyme is responsible for unwinding the DNA double helix during replication?

Accepted Answer

DNA helicase

Question 14

A patient is exposed to UV light, resulting in the formation of thymine dimers. Which repair system is most likely to be activated?

Accepted Answer

Nucleotide excision repair

Question 15

Which of the following equations correctly represents the formation of a phosphodiester bond during DNA synthesis?

Accepted Answer

$$dNTP + (DNA)_{n} \rightarrow (DNA)_{n+1} + PP_i$$

Question 16

Which of the following is NOT a function of DNA polymerase during replication?

Accepted Answer

Joining Okazaki fragments

Question 17

In mismatch repair, which protein in E. coli recognizes and binds to the mismatched base pair?

Accepted Answer

MutS

Question 18

Which of the following statements about Okazaki fragments is TRUE?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand.

Question 19

A nonsense mutation in a gene is most likely to result in:

Accepted Answer

A truncated, usually inactive protein

Question 20

Which of the following best describes the role of primase during DNA replication?

Accepted Answer

It synthesizes short RNA primers to provide a starting point for DNA polymerase.

DNA Replication, Mutation, and DNA Repair: Study Notes for Genetics

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