Question 1

Which of the following best describes the role of CENP-A at the centromere?

Accepted Answer

CENP-A replaces histone H3 in nucleosomes at the centromere, creating a unique chromatin structure recognized by kinetochore proteins.

Question 2

A mutation that disrupts the shelterin complex at telomeres would most likely result in which cellular phenotype?

Accepted Answer

Increased chromosome end-to-end fusions due to misrecognition of telomeres as DNA breaks.

Question 3

Which of the following is a direct consequence of the 'end replication problem' in eukaryotic cells?

Accepted Answer

Progressive shortening of chromosome ends with each cell division.

Question 4

Which enzyme is responsible for adding telomeric repeats to chromosome ends, and what is its unique biochemical activity?

Accepted Answer

Telomerase; it is a reverse transcriptase that uses an RNA template to synthesize DNA.

Question 5

Which of the following histone modifications is most strongly associated with heterochromatin?

Accepted Answer

H3K9me3

Question 6

A researcher observes that a gene is highly expressed and its chromatin is sensitive to DNase I digestion. Which chromatin state is this gene most likely found in?

Accepted Answer

Euchromatin

Question 7

Which of the following best explains why normal human somatic cells stop dividing after 40-60 population doublings?

Accepted Answer

Telomere shortening leads to replicative senescence.

Question 8

Which of the following is a function of the condensin complex during mitosis?

Accepted Answer

Condensin organizes and compacts chromatin into mitotic chromosomes by forming loops of characteristic sizes.

Question 9

Which of the following statements about the kinetochore is correct?

Accepted Answer

The outer kinetochore assembles only during mitosis and links the chromosome to microtubules.

Question 10

Which of the following best describes the difference between constitutive and facultative heterochromatin?

Accepted Answer

Constitutive heterochromatin is always compacted in all cells, while facultative heterochromatin is compacted only in certain cells or conditions.

Question 11

Which of the following is a direct effect of histone acetylation on chromatin structure?

Accepted Answer

It neutralizes positive charges on lysine residues, reducing histone-DNA interactions and promoting open chromatin.

Question 12

Which of the following best explains why highly repetitive DNA regions are often heterochromatized?

Accepted Answer

To suppress recombination and maintain genome stability.

Question 13

Which of the following is true regarding the transcription of eukaryotic protein-coding genes?

Accepted Answer

Each gene is typically transcribed as a single transcription unit, and the initial transcript contains both coding and non-coding sequences.

Question 14

Which of the following best describes the function of the TATA-binding protein (TBP) in transcription initiation?

Accepted Answer

TBP induces a sharp bend in the DNA, facilitating the assembly of the preinitiation complex.

Question 15

Which of the following is a key difference between RNA polymerase II and DNA polymerase?

Accepted Answer

RNA polymerase II does not require a primer to initiate synthesis, while DNA polymerase does.

Question 16

Which of the following best explains the role of positive feedback in the propagation of histone modifications?

Accepted Answer

Enzymes that add specific modifications can bind to those same modifications, spreading the mark along the chromosome.

Question 17

Which of the following is a plausible reason why the spread of a histone modification does NOT cover an entire chromosome?

Accepted Answer

Boundary elements or competing modifications can block the spread of a given histone mark.

Question 18

Which of the following best describes the relationship between A and B compartments in the nucleus?

Accepted Answer

A compartments are euchromatic and transcriptionally active, while B compartments are heterochromatic and transcriptionally silent.

Question 19

Which of the following is a direct function of the 3' overhang at telomeres?

Accepted Answer

It can invade upstream double-stranded telomeric repeats to form a T-loop, protecting chromosome ends.

Nucleus: Gene Expression and Chromatin Structure

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