Question 1

Which of the following best describes a frameshift mutation, and what is its likely effect on the resulting protein?

Accepted Answer

An insertion or deletion of one or more base pairs that alters the reading frame, often resulting in a nonfunctional protein.

Question 2

A patient is exposed to a chemical that causes the loss of a purine base from DNA. What is this type of DNA damage called, and what is the most likely consequence during DNA replication?

Accepted Answer

Depurination; DNA polymerase may insert a random nucleotide at the site, potentially causing a mutation.

Question 3

Which of the following mutations is most likely to result from the action of an intercalating agent such as proflavin?

Accepted Answer

Frameshift mutation

Question 4

A DNA sequence undergoes a tautomeric shift during replication. Which of the following best explains how this can lead to a permanent mutation?

Accepted Answer

The tautomeric shift allows a base to pair with a non-complementary base, which, if not corrected, becomes a permanent base-pair change after the next round of replication.

Question 5

Which of the following best describes the difference between a transition and a transversion mutation?

Accepted Answer

A transition is a change from a purine to another purine or a pyrimidine to another pyrimidine, while a transversion is a change from a purine to a pyrimidine or vice versa.

Question 6

A researcher exposes bacterial cells to UV light, resulting in the formation of thymine dimers. Which DNA repair mechanism is directly responsible for reversing this specific damage in bacteria?

Accepted Answer

Photoreactivation repair

Question 7

Which of the following is a key feature of the SOS repair system in E. coli?

Accepted Answer

It allows DNA replication to continue past lesions but is error-prone and can introduce mutations.

Question 8

A mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; results in premature termination of translation.

Question 9

Which of the following best explains why repeated DNA sequences are hotspots for certain hereditary diseases such as Huntington’s disease?

Accepted Answer

They are prone to replication slippage, leading to insertions or deletions.

Question 10

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

Accepted Answer

Endonuclease cuts the DNA, DNA polymerase fills the gap, DNA ligase seals the nick.

Question 11

A patient with a genetic disorder is found to have a mutation that only manifests at elevated temperatures. What type of mutation is this?

Accepted Answer

Conditional/temperature-sensitive mutation

Question 12

Which of the following best describes the effect of oxidative damage on DNA?

Accepted Answer

It can modify guanine to 8-oxoguanine, which mispairs with adenine, leading to point mutations.

Question 13

Which of the following statements about mutagens is correct?

Accepted Answer

Mutagens can be natural or artificial agents that increase the frequency of mutations.

Question 14

A DNA repair system removes a short segment of nucleotides containing a bulky lesion and fills the gap using DNA polymerase and ligase. What is this repair mechanism called?

Accepted Answer

Nucleotide excision repair (NER)

Question 15

Which of the following best explains why the reduction of $$O_2 to $$water in mitochondria is not 100% efficient and how this relates to mutation?

Accepted Answer

Some $$O_2 is $$converted to superoxide radicals ($$O_2$$^-$$), which are highly reactive and can cause oxidative DNA damage leading to mutations.

Question 16

Which of the following is NOT a possible outcome of a gene mutation?

Accepted Answer

Guaranteed lethality in all cases

Question 17

A mutation occurs in a gene located on the X chromosome in a male. What is the most likely consequence regarding inheritance?

Accepted Answer

The mutation will be inherited by all daughters but not sons.

Question 18

Which of the following best describes a silent mutation?

Accepted Answer

A mutation that changes a codon but does not alter the amino acid sequence due to the redundancy of the genetic code.

Question 19

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

Accepted Answer

Huntington’s disease

Question 20

Which of the following best explains the role of DNA ligase in DNA repair mechanisms?

Accepted Answer

DNA ligase seals the final 'nick' in the sugar-phosphate backbone after repair synthesis.

Gene Mutation, DNA Repair, and Transposition: Study Notes for Genetics

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