Question 1

Which type of mutation results in a premature stop codon, potentially leading to a truncated protein product?

Accepted Answer

Nonsense mutation

Question 2

A parent carries a mutation in an X-linked gene in their sperm. Which statement best describes the potential for inheritance?

Accepted Answer

The mutation can be passed to both sons and daughters.

Question 3

Which of the following is an example of a transition mutation?

Accepted Answer

Guanine (G) replaced by Adenine (A)

Question 4

A DNA sequence undergoes a tautomeric shift, causing an anomalous base pairing during replication. What is the most likely outcome?

Accepted Answer

A point mutation (substitution)

Question 5

Which DNA repair mechanism is primarily responsible for correcting thymine dimers induced by UV light in humans?

Accepted Answer

Nucleotide excision repair

Question 6

A mutation occurs in a somatic cell due to exposure to nitrous acid. What is the most likely consequence regarding inheritance?

Accepted Answer

The mutation will not be inherited by offspring.

Question 7

Which of the following best describes a synonymous mutation?

Accepted Answer

A nucleotide change that does not alter the amino acid sequence

Question 8

A patient with xeroderma pigmentosum is highly sensitive to sunlight. This condition is most directly caused by defects in which process?

Accepted Answer

Nucleotide excision repair

Question 9

Which equation best represents the error rate of DNA replication in humans with proofreading?

Accepted Answer

$$3 	imes 10$$^{-9}$$

Question 10

A double-stranded break (DSB) in DNA can be repaired by homologous recombination. Which step is essential for this process?

Accepted Answer

Use of a homologous sequence as a template for repair

Question 11

Which of the following mutagens is most likely to induce a transversion mutation?

Accepted Answer

Ionizing radiation

Question 12

A DNA polymerase makes an error during replication, inserting the wrong nucleotide. Which repair mechanism is most likely to correct this error immediately?

Accepted Answer

Proofreading by DNA polymerase

Question 13

Which process can lead to spontaneous mutations in DNA without exposure to external mutagens?

Accepted Answer

Depurination

Question 14

A mutation changes the codon GAT (Asp) to TAT (Tyr). What type of mutation is this?

Accepted Answer

Missense mutation

Question 15

Which of the following statements about transposable elements (TEs) is correct?

Accepted Answer

TEs can contribute to human diseases and evolution.

Question 16

A patient is exposed to ionizing radiation, resulting in a double-stranded break in DNA. Which repair pathway is most error-prone?

Accepted Answer

Non-homologous end joining (NHEJ)

Question 17

Which of the following is a real-life example of a mutation caused by replication slippage?

Accepted Answer

Expansion of trinucleotide repeats in Huntington's disease

Question 18

Which repair mechanism involves the RecA protein and recombinational exchange to fix post-replication errors?

Accepted Answer

Postreplication repair

Question 19

A mutation in the BRCA1 gene impairs its function. What is the most likely consequence?

Accepted Answer

Increased risk of cancer due to defective DNA repair

Question 20

Which of the following best explains why bacteria require high-fidelity DNA repair mechanisms?

Accepted Answer

Bacteria are haploid, so mutations are immediately expressed and can be lethal.

Mutations and DNA Repair Mechanisms: Oct 31

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