Question 1

Which of the following best describes the molecular change responsible for sickle-cell anemia?

Accepted Answer

A base-pair change in the β-globin gene

Question 2

Depurination is a spontaneous mutation process. What is the most likely outcome if a depurinated site is not repaired before DNA replication?

Accepted Answer

A nucleotide pair deletion

Question 3

Deamination of cytosine results in the formation of uracil. If this change is not repaired, what mutation will occur after two rounds of DNA replication?

Accepted Answer

A C→T transition

Question 4

Which chemical mutagen acts by inserting itself between DNA base pairs, causing distortions and unwinding of the double helix?

Accepted Answer

Ethidium bromide

Question 5

Which of the following is a consequence of oxidative damage to DNA caused by free radicals?

Accepted Answer

Breakage of phosphodiester bonds

Question 6

Ultraviolet (UV) radiation primarily causes which type of DNA damage?

Accepted Answer

Formation of thymine dimers

Question 7

A graph shows the number of mutations induced by X-ray dose in fruit flies. What can you conclude if the number of mutations increases linearly with dose?

Accepted Answer

Any exposure to X-rays will cause mutations

Question 8

The Ames test is used to assess the mutagenic potential of chemical compounds. Which statement about the Ames test is TRUE?

Accepted Answer

It uses liver enzymes to simulate in vivo metabolism for chemicals that require activation to become mutagenic.

Question 9

You use the Ames test to evaluate a new pesticide. You observe significantly more bacterial colonies on the treatment plate than the control plate. What does this indicate?

Accepted Answer

The chemical is mutagenic and probably also carcinogenic.

Question 10

Which DNA repair mechanism is responsible for correcting small insertions or deletions caused by DNA polymerase slippage?

Accepted Answer

Mismatch Repair (MMR)

Question 11

In bacteria, how does the mismatch repair system distinguish the newly synthesized DNA strand from the template strand?

Accepted Answer

By the absence of methylation on the new strand

Question 12

Which of the following mutagens is an alkylating agent that donates alkyl groups to DNA bases?

Accepted Answer

Ethylmethylsulfonate (EMS)

Question 13

Transposable elements can cause mutations by:

Accepted Answer

Moving within the genome and creating or reversing mutations

Question 14

Which DNA repair mechanism is primarily responsible for removing pyrimidine dimers caused by UV radiation?

Accepted Answer

Nucleotide Excision Repair (NER)

Question 15

A his⁻ auxotroph cannot grow on minimal medium unless:

Accepted Answer

It mutates (reverts) back to his⁺ or is given histidine

Question 16

Which of the following is a base analog that can be incorporated into DNA and cause mutations?

Accepted Answer

5-bromouracil

Question 17

Which equation best represents the relationship between energy and wavelength in the electromagnetic spectrum?

Accepted Answer

$$E = \frac{hc}{\lambda}$$

Question 18

Which DNA repair mechanism is used to fix double-strand breaks by joining the ends without a homologous template?

Accepted Answer

Nonhomologous End Joining (NHEJ)

Question 19

If a 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 20

Which of the following statements about mutagens is correct?

Accepted Answer

Mutagens can be physical, chemical, or biological agents that induce mutations

DNA Mutation: Types, Causes, and Repair Mechanisms

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