Question 1

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

DNA is transcribed into RNA, which is then translated into protein.

Question 2

A mutation that results in the insertion of a single nucleotide pair into a gene will most likely cause which of the following?

Accepted Answer

A frameshift mutation

Question 3

Which enzyme is responsible for unwinding the DNA double helix during replication in bacteria?

Accepted Answer

Helicase

Question 4

In the lac operon of E. coli, what happens when lactose is present?

Accepted Answer

Allolactose binds to the repressor, inactivating it and allowing transcription.

Question 5

Which of the following is a function of plasmids in bacteria?

Accepted Answer

They may carry genes for antibiotic resistance and can be transferred horizontally.

Question 6

A base substitution mutation changes a codon from $$	ext{UAC} ($$tyrosine) to $$	ext{UAA} ($$stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 7

Which of the following statements about bacterial DNA replication is correct?

Accepted Answer

Replication is bidirectional and each daughter cell receives one copy of the DNA molecule.

Question 8

Which of the following best describes the function of tRNA during translation?

Accepted Answer

It transports specific amino acids to the ribosome and matches them to the mRNA codon.

Question 9

Which of the following is an example of horizontal gene transfer in bacteria?

Accepted Answer

A bacterium taking up naked DNA from the environment and incorporating it into its genome.

Question 10

Which of the following mutagens causes adenine to pair with cytosine instead of thymine?

Accepted Answer

Nitrous acid

Question 11

What is the role of the operator in an operon?

Accepted Answer

It is the DNA segment where the repressor can bind to regulate transcription.

Question 12

Which of the following best explains why the genetic code is described as 'degenerate'?

Accepted Answer

Some amino acids are coded by more than one codon.

Question 13

A bacterial cell is exposed to UV light, resulting in the formation of thymine dimers. Which repair mechanism can directly reverse this damage?

Accepted Answer

Photolyase (light repair enzyme)

Question 14

Which of the following is true about repressible operons such as the trp operon?

Accepted Answer

They are usually on and are turned off when a corepressor is present.

Question 15

Which of the following best describes generalized transduction?

Accepted Answer

A bacteriophage transfers random bacterial DNA fragments to a recipient cell.

Question 16

Which of the following is a likely consequence of a frameshift mutation in a gene?

Accepted Answer

The reading frame is altered, changing many downstream amino acids.

Question 17

Which of the following is the best definition of an auxotroph?

Accepted Answer

A mutant that has a nutritional requirement absent in the parent.

Question 18

Which of the following statements about conjugation in bacteria is correct?

Accepted Answer

It requires direct cell-to-cell contact and involves the transfer of plasmid DNA.

Question 19

Which of the following is a function of transposons?

Accepted Answer

They move from one region of DNA to another and may inactivate genes.

Question 20

Which of the following best describes the Ames test?

Accepted Answer

It uses bacteria to test whether a substance is a mutagen by measuring the rate of mutation reversion.

Microbial Genetics: Structure, Function, and Variation

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