Question 1

Which of the following best describes a frameshift mutation and its likely effect on a protein-coding gene?

Accepted Answer

An insertion or deletion of nucleotides that is not a multiple of three, altering the reading frame and potentially changing every amino acid downstream.

Question 2

A mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 3

Which of the following is a real-world example of heterozygote advantage in human populations?

Accepted Answer

Individuals with one sickle-cell allele and one normal allele are more likely to survive malaria than either homozygote.

Question 4

Which of the following mutations is most likely to have the least severe effect on the phenotype of a protein-coding gene?

Accepted Answer

Missense substitution

Question 5

A mutation in gene X overrides the effect of a previous mutation in gene Y and restores the wild-type phenotype. What is the mutation in gene X called?

Accepted Answer

Intergenic suppressor mutation

Question 6

Which of the following best describes a transition mutation?

Accepted Answer

A pyrimidine is replaced by another pyrimidine, or a purine is replaced by another purine.

Question 7

If the cytosine in the sequence TCAT is deaminated and not repaired, which point mutation would you observe after two rounds of DNA replication?

Accepted Answer

TAAT

Question 8

Which of the following types of mutations will NOT be passed to offspring?

Accepted Answer

Somatic

Question 9

Which of the following is a consequence of depurination if the lesion is not repaired before DNA replication?

Accepted Answer

A nucleotide pair is lost, or an incorrect nucleotide (often adenine) is inserted opposite the apurinic site.

Question 10

Which of the following best describes a dominant-negative mutation?

Accepted Answer

A mutation where the mutant protein interferes with the function of the wild-type protein, causing a dominant phenotype.

Question 11

Which of the following is true about somatic mutations?

Accepted Answer

They occur in body cells and are not passed to offspring.

Question 12

A mutation changes a sense codon into a synonymous codon, leaving the amino acid sequence unchanged. What type of mutation is this?

Accepted Answer

Silent mutation

Question 13

Which of the following best explains why the sickle-cell allele remains prevalent in certain populations despite its harmful effects in homozygotes?

Accepted Answer

Heterozygotes have a survival advantage in regions where malaria is common.

Question 14

Which of the following is a real-life example of a conditional mutation?

Accepted Answer

A mutation that causes a disease phenotype only at high temperatures.

Question 15

Which of the following best describes a neutral mutation?

Accepted Answer

A mutation that changes the amino acid sequence but does not affect protein function.

Question 16

Which of the following is the correct chromosome number in a human gamete?

Accepted Answer

23

Question 17

Which of the following best describes a missense mutation?

Accepted Answer

A mutation that changes a codon to code for a different amino acid.

Question 18

Which of the following is a likely outcome of a tautomeric shift during DNA replication?

Accepted Answer

A transition mutation in the complementary strand.

Question 19

Which of the following best describes an intergenic suppressor mutation?

Accepted Answer

A mutation that occurs in a different gene and suppresses the effect of the original mutation.

Question 20

Which of the following is a characteristic of a loss-of-function mutation?

Accepted Answer

It results in a complete or partial loss of gene function.

DNA Mutation and Repair: Types, Mechanisms, and Genetic Implications

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