Question 1

Which of the following best describes a spontaneous mutation?

Accepted Answer

A mutation that arises from normal biological or chemical processes that alter nitrogenous bases.

Question 2

Replication slippage is most likely to occur in which type of DNA sequence, and what is a potential consequence?

Accepted Answer

In repeat sequences, leading to small insertions or deletions.

Question 3

Tautomeric shifts in DNA bases can result in which of the following outcomes?

Accepted Answer

Permanent base-pair changes due to noncomplementary base pairing during replication.

Question 4

Depurination and deamination are both examples of:

Accepted Answer

Spontaneous DNA base damage leading to mutations.

Question 5

Which chemical change occurs during deamination of cytosine?

Accepted Answer

Cytosine is converted to uracil.

Question 6

Free radicals can cause DNA damage by which of the following mechanisms?

Accepted Answer

Directly breaking phosphodiester bonds and altering bases.

Question 7

Base analogs such as 5-bromouracil increase mutation rates by:

Accepted Answer

Mimicking normal DNA bases and increasing the frequency of tautomeric shifts.

Question 8

Which of the following best describes the action of intercalating agents?

Accepted Answer

They wedge between DNA base pairs, causing distortions and unwinding.

Question 9

Ultraviolet (UV) light primarily causes which type of DNA damage?

Accepted Answer

Formation of pyrimidine dimers, especially thymine dimers.

Question 10

Which DNA repair mechanism is responsible for removing and replacing incorrectly inserted nucleotides during replication?

Accepted Answer

Proofreading by DNA polymerase.

Question 11

Strand discrimination during mismatch repair in bacteria is based on:

Accepted Answer

DNA methylation status, where the newly synthesized strand is unmethylated.

Question 12

A patient with xeroderma pigmentosum is most likely to have a defect in which DNA repair pathway?

Accepted Answer

Nucleotide excision repair (NER).

Question 13

Which of the following statements about the SOS repair system in E. coli is correct?

Accepted Answer

It is an error-prone repair system that allows replication to continue past DNA damage.

Question 14

Which of the following is true regarding homologous recombination repair of double-strand breaks?

Accepted Answer

It uses a sister chromatid as a template to accurately repair the break.

Question 15

Transposable elements can cause mutations by:

Accepted Answer

Inserting into coding or regulatory regions, disrupting gene function or expression.

Question 16

In the Ac-Ds system in maize, what is the role of the Ac (Activator) element?

Accepted Answer

It provides the necessary gene products for the Ds (Dissociation) element to transpose.

Question 17

Which of the following best explains why P element transposition in Drosophila leads to hybrid dysgenesis only in certain crosses?

Accepted Answer

M strain females lack the suppressor protein, so P element transposition is not controlled in their eggs.

Question 18

Which of the following is a real-world example of a disease caused by replication slippage in repeat sequences?

Accepted Answer

Huntington disease.

Question 19

Which of the following equations correctly represents the mutation rate ($$\mu) $$per gene per generation if 4 mutations are observed in $$1 	imes 10^9$ gametes?

Accepted Answer

$$\mu = \frac{4}{1 	imes 10^9$}$$

Question 20

Which of the following statements about base excision repair (BER) is correct?

Accepted Answer

DNA glycosylase recognizes and removes the altered base, followed by endonuclease cutting the DNA backbone.

Mutation and DNA Repair Mechanisms in Genetics

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