Question 1

Which of the following best describes the function of plasmids in bacterial cells?

Accepted Answer

They are self-replicating circular DNA molecules that often carry genes enhancing bacterial pathogenicity.

Question 2

During DNA replication, which enzyme is responsible for joining Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 3

A mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 4

Which of the following statements about the central dogma of molecular biology is correct?

Accepted Answer

It describes the flow of genetic information from DNA to RNA to protein.

Question 5

Which process is illustrated by the following equation? 
$$	ext{DNA} \xrightarrow{	ext{RNA polymerase}} 	ext{RNA}$$

Accepted Answer

Transcription

Question 6

In the lac operon, what happens when both glucose and lactose are present in the environment?

Accepted Answer

The lac operon is not strongly expressed due to catabolite repression.

Question 7

Which of the following best explains why DNA replication is considered semi-conservative?

Accepted Answer

Each new DNA molecule consists of one parental and one newly synthesized strand.

Question 8

A bacterial cell is exposed to nitrous acid, which causes adenine to pair with cytosine instead of thymine. What is the most likely outcome?

Accepted Answer

An increased mutation rate due to base substitution errors.

Question 9

Which of the following is a key difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

In eukaryotes, transcription occurs in the nucleus and translation in the cytoplasm.

Question 10

Which of the following best describes a frameshift mutation?

Accepted Answer

An insertion or deletion of one or more nucleotide pairs that shifts the reading frame.

Question 11

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

Accepted Answer

Helicase

Question 12

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

Accepted Answer

Transfer of a plasmid from one cell to another via conjugation.

Question 13

Which of the following best describes the role of cAMP in the regulation of the lac operon?

Accepted Answer

cAMP binds to CAP, which then binds to the promoter to enhance transcription when glucose is low.

Question 14

Which of the following is a function of microRNAs (miRNAs) in post-transcriptional regulation?

Accepted Answer

They base pair with mRNA, making it double-stranded and targeting it for enzymatic destruction.

Question 15

A scientist wants to test whether a chemical is mutagenic. Which method should they use?

Accepted Answer

Ames test

Question 16

Which of the following best describes the function of transposons?

Accepted Answer

They are mobile genetic elements that can move genes, such as antibiotic resistance, between DNA molecules.

Question 17

Which of the following is true about repressible operons?

Accepted Answer

They are usually on but can be turned off by a corepressor.

Question 18

Which of the following best explains why DNA polymerase has a low error rate during replication?

Accepted Answer

It has proofreading activity that corrects mismatched bases.

Question 19

Which of the following is a clinical application of genomics?

Accepted Answer

Identifying antibiotic resistance genes in pathogens to guide treatment.

Question 20

Which of the following best describes the difference between genotype and phenotype?

Accepted Answer

Genotype is the genetic makeup; phenotype is the observable trait.

Microbial Genetics: Structure, Function, and Regulation

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