Question 1

Which of the following best describes the mechanism by which allolactose induces the lac operon in E. coli?

Accepted Answer

Allolactose binds to the LacI repressor protein, causing a conformational change that prevents it from binding to the operator.

Question 2

A bacterial cell is grown in the presence of both glucose and lactose. Which of the following best describes the expected transcriptional activity of the lac operon?

Accepted Answer

No transcription, because glucose inhibits cAMP production, preventing CAP from activating the operon.

Question 3

Which of the following statements about enhancers in eukaryotic gene regulation is TRUE?

Accepted Answer

Enhancers can function at variable distances and orientations relative to the gene, and can affect more than one gene.

Question 4

A mutation changes a codon from $$\mathrm{GAG} ($$glutamic acid) to $$\mathrm{GTG} ($$valine) in the $$\beta-$$globin gene. This is an example of:

Accepted Answer

A missense mutation

Question 5

Which of the following best explains why cAMP levels are low in the presence of glucose, affecting the lac operon?

Accepted Answer

Glucose inhibits the enzyme adenylate cyclase, reducing cAMP synthesis.

Question 6

A patient is diagnosed with Cri-du-chat syndrome. Which chromosomal abnormality is most likely responsible for this condition?

Accepted Answer

A deletion of a segment on chromosome 5

Question 7

Which of the following scenarios best illustrates the concept of a suppressor mutation?

Accepted Answer

A mutation in a different gene compensates for the phenotype caused by the original mutation.

Question 8

Which of the following is a key difference between promoters and enhancers in eukaryotic gene regulation?

Accepted Answer

Enhancers can be located far from the gene they regulate, while promoters are typically adjacent to the transcription start site.

Question 9

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

Accepted Answer

An insertion or deletion of one base pair

Question 10

In the trp operon, what is the role of tryptophan in regulating gene expression?

Accepted Answer

Tryptophan binds to the TrpR repressor, enabling it to bind the operator and block transcription.

Question 11

Alternative splicing in eukaryotes allows for:

Accepted Answer

The production of multiple proteins from a single gene by combining exons in different ways.

Question 12

Which of the following is an example of catabolite repression in bacteria?

Accepted Answer

The presence of glucose inhibits cAMP synthesis, reducing activation of multiple operons.

Question 13

Familial Down Syndrome is most commonly caused by which chromosomal event?

Accepted Answer

Non-reciprocal translocation between chromosome 21 and another non-homologous chromosome

Question 14

Which of the following best describes the function of anti-sense RNA in gene regulation?

Accepted Answer

It binds to complementary mRNA sequences, blocking translation.

Question 15

A true revertant mutation is best defined as:

Accepted Answer

A mutation that restores the original DNA sequence at the site of the original mutation.

Question 16

Which of the following is an example of polyploidy leading to speciation?

Accepted Answer

The formation of bread wheat from hybridization events between different species.

Question 17

Which of the following best explains why the lac operon is not expressed at high levels when both glucose and lactose are present?

Accepted Answer

Glucose inhibits cAMP production, so CAP cannot activate transcription even if lactose is present.

Question 18

A patient with Fragile X syndrome most likely has which type of chromosomal abnormality?

Accepted Answer

An expansion of a trinucleotide repeat leading to a fragile site on the X chromosome

Question 19

Which of the following best describes end-product inhibition in the context of enzyme regulation?

Accepted Answer

The final product of a metabolic pathway inhibits the activity of an enzyme earlier in the pathway.

Question 20

Which of the following is a likely consequence of a nonsense mutation in a gene?

Accepted Answer

A premature stop codon is introduced, leading to a truncated protein.

Regulation of Gene Expression and Mutations: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards