Question 1

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

Accepted Answer

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

Question 2

A mutation in DNA that changes a codon from $$	ext{GGC} ($$glycine) to $$	ext{AGC} ($$serine) is an example of which type of mutation?

Accepted Answer

Missense mutation

Question 3

Which statement about plasmids is correct?

Accepted Answer

Plasmids are self-replicating circular DNA molecules that can carry antibiotic resistance genes.

Question 4

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

Accepted Answer

The inducer (allolactose) binds to the repressor, inactivating it and allowing transcription.

Question 5

Which enzyme is responsible for joining Okazaki fragments during DNA replication?

Accepted Answer

DNA ligase

Question 6

A frameshift mutation is most likely to result from which of the following?

Accepted Answer

Insertion or deletion of one or more nucleotide pairs

Question 7

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

Accepted Answer

Multiple codons can code for the same amino acid.

Question 8

In prokaryotes, why can translation begin before transcription is complete?

Accepted Answer

Transcription and translation both occur in the cytoplasm, allowing ribosomes to access mRNA as it is being synthesized.

Question 9

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

Accepted Answer

They bind to mRNA, forming double-stranded RNA that is enzymatically destroyed, preventing protein production.

Question 10

Which of the following statements about the Ames test is correct?

Accepted Answer

It uses a histidine auxotroph to detect the reversion rate after exposure to a mutagen.

Question 11

Which process involves the transfer of 'naked' DNA from one bacterium to another?

Accepted Answer

Transformation

Question 12

What is the role of cAMP in catabolite repression of the lac operon?

Accepted Answer

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

Question 13

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

Accepted Answer

Excess end-product acts as a corepressor, activating the repressor to stop transcription.

Question 14

Which of the following best describes vertical gene transfer?

Accepted Answer

Transfer of genes from one organism to its offspring during reproduction.

Question 15

A chemical mutagen that causes adenine to pair with cytosine instead of thymine is most likely:

Accepted Answer

Nitrous acid

Question 16

Which repair mechanism uses light to separate thymine dimers caused by UV radiation?

Accepted Answer

Photolyase (light-repair enzyme)

Question 17

Which of the following is a consequence of a nonsense mutation?

Accepted Answer

A stop codon is created, leading to premature termination of translation.

Question 18

Which of the following is true about conjugation in Gram-negative bacteria?

Accepted Answer

It requires a sex pilus encoded by a conjugative plasmid.

Question 19

Which of the following is a function of transposons?

Accepted Answer

They can move genes, such as antibiotic resistance, from one DNA region to another.

Question 20

How do mutations and genetic recombination contribute to evolution?

Accepted Answer

They create cell diversity, providing raw material for natural selection.

Microbial Genetics: Study Notes (Chapter 8, Microbiology: An Introduction)

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