Question 1

When guanine shifts to its rare enol form during DNA replication, which nucleotide can DNA polymerase incorporate opposite it, and what base pair will result in the mutant cell after two rounds of replication?

Accepted Answer

DNA polymerase incorporates thymine, resulting in an A·T base pair.

Question 2

Oxidation of guanine to 8-oxoguanine can lead to which type of base pair substitution after DNA replication?

Accepted Answer

$$\mathrm{G \cdot C \rightarrow T \cdot A}$$ transversion

Question 3

Which of the following best describes the mutational event caused by the incorporation of 2-aminopurine (2-AP) into DNA, followed by its protonation during replication?

Accepted Answer

$$\mathrm{A \cdot T \rightarrow G \cdot C}$$

Question 4

A wild-type DNA sequence is $$\ldots \mathrm{CTTGCAAGCGAATC} \ldots$$ and a mutant sequence is $$\ldots \mathrm{CTTGCTAGCGAATC} \ldots. $$The substitution appears to create a stop codon. What additional information is needed to confirm this?

Accepted Answer

The reading frame and the genetic code for the organism.

Question 5

Can a G·C → A·T transition-causing mutagen induce a proline-to-histidine missense mutation? Use the genetic code to justify your answer.

Accepted Answer

No, because the codons for proline and histidine differ by more than a single G·C → A·T transition.

Question 6

Where within a gene might trinucleotide repeat expansion occur, and how can this lead to disease?

Accepted Answer

In coding or regulatory regions; expansion can disrupt protein function or gene expression, causing diseases like Huntington's.

Question 7

Why are many chemicals that test positive in the Ames test also classified as carcinogens?

Accepted Answer

Because mutagenicity is often correlated with carcinogenicity, as mutations can lead to cancer.

Question 8

Which of the following best differentiates between transitions and transversions?

Accepted Answer

Transitions are purine-to-purine or pyrimidine-to-pyrimidine changes; transversions are purine-to-pyrimidine or vice versa.

Question 9

Which of the following is NOT possible? (Select all that apply)

Accepted Answer

A frameshift mutation in a regulatory region

Question 10

A missense mutation changes a proline codon (CCU, CCC, CCA, or CCG) to a serine codon (UCU, UCC, UCA, UCG, AGU, or AGC). Can this be caused by a G·C → A·T transition?

Accepted Answer

Yes, if the mutation changes the third position of CCG to UCG.

Question 11

Which of the following best describes a frameshift mutation?

Accepted Answer

An insertion or deletion that alters the reading frame of a gene.

Question 12

Which of the following is a likely consequence of an alkylating agent such as EMS reacting with guanine in DNA?

Accepted Answer

Formation of O-6-ethylguanine, leading to a $$\mathrm{G \cdot C \rightarrow A \cdot T}$$ transition.

Question 13

Which of the following best differentiates between synonymous and neutral mutations?

Accepted Answer

Synonymous mutations do not change the amino acid; neutral mutations do not affect protein function.

Question 14

Which of the following best describes the difference between missense and nonsense mutations?

Accepted Answer

Missense mutations change one amino acid to another; nonsense mutations create a premature stop codon.

Question 15

Which of the following best describes the difference between frameshift and nonsense mutations?

Accepted Answer

Frameshift mutations alter the reading frame; nonsense mutations introduce a stop codon.

Question 16

Which of the following types of DNA damage is most likely to result in spontaneous his+ revertant colonies in a bacterial Ames test?

Accepted Answer

Depurination or deamination leading to base substitutions that restore gene function.

Question 17

Which of the following types of mutations in a new mutant allele could explain the absence of mRNA in a Northern blot of heterozygous Drosophila?

Accepted Answer

Nonsense or deletion mutations.

Question 18

Which of the following best describes the molecular mechanism by which intercalating agents induce mutations?

Accepted Answer

They insert between base pairs, causing insertions or deletions during replication.

Question 19

Which of the following is a real-world example of a disease caused by trinucleotide repeat expansion?

Accepted Answer

Huntington's disease

Genetics Problem Set: Mutation – Causes & Consequences (Step-by-Step Guidance)

Guida di studio - Domande di pratica

Study guide - Flashcard