Q: Which of the following scenarios would most likely result in the inability of E. coli to utilize lactose as a carbon source?

A mutation in the lacZ gene ($$Z^-) $$preventing $$eta-$$galactosidase production.

Q: Which of the following equations best represents the maintenance of DNA methylation during replication?

$$\text{Methylation}_{\text{new}} = \text{DNMT} \times \text{Hemimethylated DNA}$$

Question 1

Which of the following best describes the function of the lac operon in E. coli?

Accepted Answer

It coordinates the expression of genes required for lactose metabolism in response to environmental lactose.

Question 2

A mutation in the lacI gene that prevents the repressor from binding lactose would most likely result in which phenotype?

Accepted Answer

No expression of the lac operon, even when lactose is present.

Question 3

Which of the following equations best represents the relationship between the rate of mRNA production ($$R$$), the affinity of RNA polymerase for the promoter ($$K_p$$), and the presence of a repressor ($$I) in a $$simple operon system?

Accepted Answer

$$R = \frac{K_p}{1 + I}$$

Question 4

Which of the following is a direct effect of DNA methylation at CpG islands in eukaryotic promoters?

Accepted Answer

Recruitment of proteins that condense chromatin and repress transcription.

Question 5

A bacterial cell has the following genotype: $$I^s O^+ Z^+ Y^+. $$What is the expected expression pattern of the lac operon in the presence of lactose?

Accepted Answer

No expression of lac genes.

Question 6

Which of the following statements about histone acetylation is correct?

Accepted Answer

Histone acetylation is associated with increased gene expression due to chromatin relaxation.

Question 7

Which of the following best explains why X chromosome inactivation is considered an epigenetic phenomenon?

Accepted Answer

It involves heritable changes in gene expression without altering the DNA sequence.

Question 8

A mutation in the operator region of the lac operon (Oc) results in which of the following?

Accepted Answer

The repressor protein cannot bind, leading to constitutive expression of the operon.

Question 9

Which of the following is a key difference between gene regulation in prokaryotes and eukaryotes?

Accepted Answer

Prokaryotes use operons for coordinated gene regulation, while eukaryotes typically regulate genes individually.

Question 10

Which of the following best describes the role of chromatin remodeling complexes such as SWI/SNF in eukaryotic gene regulation?

Accepted Answer

They use ATP to reposition nucleosomes, making DNA more or less accessible to transcription machinery.

Question 11

Which of the following scenarios would most likely result in the inability of E. coli to utilize lactose as a carbon source?

Accepted Answer

A mutation in the lacZ gene ($$Z^-) $$preventing $$eta-$$galactosidase production.

Question 12

Which of the following equations best represents the maintenance of DNA methylation during replication?

Accepted Answer

$$	ext{Methylation}_{	ext{new}} = 	ext{DNMT} 	imes 	ext{Hemimethylated DNA}$$

Question 13

Which of the following is a real-life example of epigenetic regulation at the chromosome level?

Accepted Answer

X chromosome inactivation in female mammals.

Question 14

Which of the following best explains the molecular basis of Prader-Willi and Angelman syndromes?

Accepted Answer

They result from deletions and epigenetic silencing of specific genes on chromosome 15, with the parent of origin determining the syndrome.

Question 15

Which of the following statements about polycistronic mRNA is correct?

Accepted Answer

It is a feature of prokaryotic operons and encodes multiple proteins from a single mRNA.

Question 16

Which of the following is a plausible outcome of a mutation that inactivates the histone acetyltransferase (HAT) enzyme in a eukaryotic cell?

Accepted Answer

Decreased gene expression due to more condensed chromatin.

Question 17

Which of the following best describes the effect of allolactose on the lac operon?

Accepted Answer

It acts as an inducer by binding to the repressor, causing it to release from the operator.

Question 18

Which of the following is NOT a mechanism of epigenetic regulation?

Accepted Answer

Alternative splicing.

Gene Regulation in Prokaryotes and Eukaryotes: The Lac Operon and Epigenetic Mechanisms

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