Question 1

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

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

Question 2

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

Accepted Answer

Nonsense mutation; introduces a premature stop codon.

Question 3

Which enzyme is responsible for removing RNA primers and replacing them with DNA during bacterial DNA replication?

Accepted Answer

DNA polymerase I

Question 4

In the lac operon, what two conditions must be met for the operon to be fully active and transcribed?

Accepted Answer

Glucose absent and lactose present

Question 5

Which of the following statements about Okazaki fragments is TRUE?

Accepted Answer

They are joined together by DNA ligase.

Question 6

A bacterial cell is exposed to UV light, resulting in the formation of thymine dimers. Which DNA repair mechanism is most likely to fix this damage?

Accepted Answer

Nucleotide-excision repair

Question 7

Which of the following best describes the function of the Shine-Dalgarno sequence in prokaryotic translation?

Accepted Answer

It is the site where the ribosome binds to initiate translation.

Question 8

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

Accepted Answer

Eukaryotic mRNA undergoes splicing to remove introns.

Question 9

A scientist discovers a bacterial strain that can take up naked DNA from its environment and incorporate it into its genome. This process is known as:

Accepted Answer

Transformation

Question 10

Which of the following best explains why frameshift mutations are often more severe than point mutations?

Accepted Answer

Frameshift mutations alter the reading frame, potentially changing every amino acid downstream.

Question 11

Which of the following is TRUE regarding the role of methylation in bacterial DNA?

Accepted Answer

It is involved in the initiation of DNA replication and protection against viral infection.

Question 12

A scientist uses the Ames test to screen a chemical for mutagenicity. Which result would indicate that the chemical is a mutagen?

Accepted Answer

Colonies of revertant (his+) Salmonella appear on the medium lacking histidine.

Question 13

Which of the following is a function of the enzyme gyrase during DNA replication?

Accepted Answer

Removes supercoils by cutting and rejoining DNA strands.

Question 14

Which of the following statements about transposons is correct?

Accepted Answer

They are segments of DNA that can move from one location to another within the same or different DNA molecule.

Question 15

During translation, which site on the ribosome does the incoming aminoacyl-tRNA first bind?

Accepted Answer

A site

Question 16

Which of the following best describes the role of the F plasmid in bacterial conjugation?

Accepted Answer

It carries genes for the formation of sex pili and mediates DNA transfer.

Question 17

A DNA template strand has the sequence 3'-TACGGTACG-5'. What is the corresponding mRNA sequence?

Accepted Answer

5'-AUGCCAUGC-3'

Question 18

Which of the following is a characteristic of repressible operons such as the trp operon?

Accepted Answer

They are usually active and can be turned off by a corepressor.

Question 19

Which of the following best explains why RNA viruses are an exception to the central dogma of genetics?

Accepted Answer

Their genetic information can be directly translated into protein without DNA.

Question 20

Which of the following is TRUE about the role of regulatory RNAs (such as miRNAs and siRNAs) in gene expression?

Accepted Answer

They inhibit translation by binding to complementary mRNA sequences.

Microbial Genetics: Structure, Replication, and Gene Function

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