Q: Which of the following equations correctly represents the overall probability of a mismatched base being incorporated and not corrected during DNA replication, given the following error rates: DNA polymerase error rate $$= 10$$^{-5}$$, proofreading correction $$= $$10^{-2}$$, and mismatch repair $$= 10$$^{-3}$$?

$$10^{-5}$$ \times $$10^{-2}$$ \times $$10^{-3}$$

Question 1

Which of the following best describes a frameshift mutation?

Accepted Answer

A mutation that results in the insertion or deletion of one or two bases, altering the reading frame of the gene

Question 2

A patient is diagnosed with Duchenne muscular dystrophy. Genetic analysis reveals a single base insertion in the DMD gene. What is the most likely consequence of this mutation at the protein level?

Accepted Answer

The protein will be truncated due to a frameshift, resulting in loss of function

Question 3

Which of the following equations correctly represents the overall probability of a mismatched base being incorporated and not corrected during DNA replication, given the following error rates: DNA polymerase error rate $$= 10$$^{-5}$$, proofreading correction $$= $$10^{-2}$$, and mismatch repair $$= 10$$^{-3}$$?

Accepted Answer

$$10^{-5}$$ 	imes $$10^{-2}$$ 	imes $$10^{-3}$$

Question 4

A missense mutation in the beta-globin gene causes sickle cell disease. Which amino acid change is responsible for this condition?

Accepted Answer

Glutamic acid to valine

Question 5

Which of the following best explains why Huntington’s disease is classified as a 'triplet expansion' disease?

Accepted Answer

It is caused by an increase in the number of CAG repeats in the HD gene

Question 6

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

Accepted Answer

A mutation in the gene for pigment production in Himalayan rabbits, resulting in dark fur only in cold body regions

Question 7

Which of the following best describes the result of a nonsense mutation?

Accepted Answer

A codon for an amino acid is changed to a stop codon, resulting in premature termination of translation

Question 8

The Luria-Delbruck fluctuation test demonstrated that mutations in bacteria arise:

Accepted Answer

Randomly, before exposure to selective pressure

Question 9

Which of the following is a likely effect of a base substitution in the promoter region of the human beta-globin gene?

Accepted Answer

Reduced or eliminated expression of the beta-globin protein

Question 10

Which DNA repair mechanism specifically recognizes and removes uracil from DNA, which can arise from spontaneous deamination of cytosine?

Accepted Answer

Base excision repair

Question 11

A chemical that inserts itself between DNA bases and causes a single base insertion during replication is best described as:

Accepted Answer

An intercalating agent

Question 12

Which of the following best explains why individuals with xeroderma pigmentosum (XP) are highly sensitive to sunlight?

Accepted Answer

They lack the ability to repair thymine dimers caused by UV light

Question 13

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

Accepted Answer

A change from cytosine to thymine

Question 14

A base analog such as 5-bromouracil can cause mutations by:

Accepted Answer

Being incorporated into DNA in place of thymine and mispairing with guanine

Question 15

Which of the following best describes the effect of a silent (synonymous) mutation?

Accepted Answer

No change in the amino acid sequence of the protein

Question 16

Which DNA repair mechanism uses the methylation state of DNA to distinguish the newly synthesized strand from the template strand in bacteria?

Accepted Answer

Mismatch repair

Question 17

A patient is found to have a reduction-of-function mutation in a gene. Which of the following is the most likely phenotype?

Accepted Answer

A partial loss of gene function, such as reduced protein activity

Question 18

Which of the following best describes the mechanism by which trinucleotide repeat expansions occur during DNA replication?

Accepted Answer

Strand slippage leads to the addition of extra repeats

Question 19

Which of the following is a likely outcome if a mutagenic chemical is found to cause a high number of revertant colonies in the Ames test using a strain that detects frameshift mutations?

Accepted Answer

The chemical likely causes frameshift mutations

Question 20

Which of the following best explains why most loss-of-function mutations are recessive?

Accepted Answer

Because one functional copy of the gene is usually sufficient to provide normal function

Mutations and Mutation Repair: Types, Mechanisms, and Biological Consequences

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