Question 1

Which of the following best describes the role of cis-acting regulatory sequences in eukaryotic gene expression?

Accepted Answer

They are DNA sequences that regulate transcription of genes on the same chromosome.

Question 2

A mutation deletes the locus control region (LCR) near the human $\beta$-globin gene complex. What is the most likely consequence?

Accepted Answer

Transcription of multiple $\beta$-globin complex genes will be abnormally regulated, potentially causing anemia.

Question 3

Which statement about enhancer and silencer sequences is correct?

Accepted Answer

Enhancers and silencers can be located far upstream, downstream, or even within the genes they regulate.

Question 4

In the yeast GAL gene system, what happens when galactose is present?

Accepted Answer

Gal3 and galactose bind Gal80, releasing Gal4 to activate transcription of GAL genes.

Question 5

Which of the following is a function of pioneer factors in eukaryotic gene regulation?

Accepted Answer

They bind regulatory DNA first, facilitating the binding of additional transcription factors.

Question 6

A patient with thalassemia has no mutations in the $\alpha$- or $\beta$-globin genes or their promoters. What is a plausible genetic explanation?

Accepted Answer

A deletion or rearrangement affecting the locus control region (LCR) near the $\beta$-globin complex.

Question 7

Which chromatin remodeling complex is primarily responsible for sliding and relocating nucleosomes to open chromatin structure?

Accepted Answer

SWI/SNF complex

Question 8

What is the effect of histone acetylation on chromatin structure and gene expression?

Accepted Answer

It relaxes chromatin, facilitating gene expression.

Question 9

Which equation best represents the relationship between the number of nucleosomes ($N$) and the length of DNA ($L$) in base pairs, given that each nucleosome covers approximately 147 bp?

Accepted Answer

$N = \frac{L}{147}$

Question 10

Which of the following is true regarding position effect variegation (PEV) in Drosophila?

Accepted Answer

PEV occurs when euchromatin is placed near heterochromatin, leading to variable gene silencing.

Question 11

Which process is directly associated with the activity of histone deacetylases (HDACs)?

Accepted Answer

Removal of acetyl groups from histone tails, leading to chromatin condensation

Question 12

In genomic imprinting, what is the role of DNA methylation at the imprinting control region (ICR) on the paternal chromosome for the IGF2/H19 locus?

Accepted Answer

It prevents insulator protein binding, silencing H19 and activating IGF2 expression.

Question 13

Which of the following best describes the function of the RISC complex in RNA interference (RNAi)?

Accepted Answer

It binds small RNA fragments and uses them to target and degrade complementary mRNA.

Question 14

A researcher uses RNAi to 'knock down' a gene in a plant. Which molecular mechanism is most likely responsible for the observed reduction in gene expression?

Accepted Answer

RNAi leads to degradation of the target mRNA via RISC-guide strand binding.

Question 15

Which of the following is a key difference between open and covered promoters in eukaryotes?

Accepted Answer

Covered promoters require nucleosome displacement for transcription to occur.

Question 16

Which protein complex is responsible for replacing histone H2A with the variant H2A.Z at the +1 nucleosome?

Accepted Answer

SWR1 complex

Question 17

Which of the following statements about epigenetic modification is FALSE?

Accepted Answer

Epigenetic modifications alter the DNA sequence.

Question 18

In the context of chromatin modification, which equation best describes the effect of acetylation on the net charge ($Q$) of a histone tail containing $n$ lysine residues, each with a charge of $+1$ before acetylation?

Accepted Answer

$Q = n - a$

Question 19

Which of the following is a direct consequence of Xist RNA expression in eutherian mammalian females?

Accepted Answer

Inactivation of one X chromosome by spreading heterochromatin and forming a Barr body.

13. Regulation of Gene Expression in Eukaryotes

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