Question 1

Which of the following best describes the function of the operator in a prokaryotic operon?

Accepted Answer

It acts as an on/off switch that controls whether the associated genes are expressed.

Question 2

In the trp operon, what is the role of tryptophan?

Accepted Answer

It acts as a corepressor that activates the repressor, shutting off transcription.

Question 3

Which of the following scenarios would result in the highest level of lac operon transcription in E. coli?

Accepted Answer

Low glucose, high lactose

Question 4

What is the effect of histone acetylation on gene expression in eukaryotes?

Accepted Answer

It causes histones to separate, generally making DNA more accessible for transcription.

Question 5

Which process is responsible for removing introns from pre-mRNA in eukaryotic cells?

Accepted Answer

RNA splicing

Question 6

How does siRNA typically regulate gene expression?

Accepted Answer

It pairs perfectly with target mRNA and leads to its cleavage and degradation.

Question 7

A stem cell that can differentiate into any cell type from any of the three germ layers, but not extra-embryonic tissue, is described as:

Accepted Answer

Pluripotent

Question 8

What is the main function of the p53 tumor suppressor gene?

Accepted Answer

It halts the cell cycle to allow DNA repair or triggers apoptosis if damage is irreparable.

Question 9

Which of the following best explains the collinearity principle of Hox genes?

Accepted Answer

The order of Hox genes on the chromosome corresponds to the anterior-to-posterior order of body regions they control.

Question 10

Which of the following is a likely consequence of a mutation that inactivates the Ras protein's GTPase activity?

Accepted Answer

Ras will remain active, continuously signaling for cell division even without growth factor.

Question 11

Which of the following best describes epigenetic inheritance?

Accepted Answer

Inheritance of gene expression patterns not involving changes to the DNA sequence.

Question 12

What is the role of enhancer sequences in eukaryotic gene regulation?

Accepted Answer

They bind activator proteins, and DNA-bending proteins bring them close to the promoter to help recruit RNA polymerase II.

Question 13

Which of the following is a function of long noncoding RNAs (lncRNAs)?

Accepted Answer

They regulate gene expression by acting as guides, scaffolds, decoys, or signals.

Question 14

Which of the following best describes the effect of DNA methylation on gene expression?

Accepted Answer

It tends to turn off (silence) the associated genes.

Question 15

A mutation in a Hox gene causes a fly to develop legs where its antennae should be. This is an example of:

Accepted Answer

A homeotic transformation

Question 16

Which of the following is a key difference between a proto-oncogene and a tumor suppressor gene?

Accepted Answer

Proto-oncogenes normally promote cell division and can become cancer-causing oncogenes when mutated; tumor suppressors like p53 normally halt division/repair damage and lose that protective function when mutated.

Question 17

Which of the following mechanisms is used by cells to rapidly respond to changes in metabolic demand?

Accepted Answer

Feedback inhibition of enzyme activity

Question 18

Which of the following best explains why HeLa cells are considered 'immortal'?

Accepted Answer

They can divide indefinitely in culture due to mutations that prevent normal cell death.

Question 19

Which of the following is a direct result of the removal of the poly-A tail from an mRNA molecule?

Accepted Answer

Decreased stability and increased degradation of the mRNA

Question 20

Which of the following best describes the role of cytoplasmic determinants in early embryonic development?

Accepted Answer

They are unevenly distributed in the egg and influence the developmental fate of daughter cells after division.

Regulation of Gene Expression: Mechanisms and Applications

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