Question 1

Which of the following correctly orders the levels of DNA packaging from least to most compact?

Accepted Answer

DNA double helix, nucleosome, chromatin fiber, looped domains, mitotic chromosome

Question 2

A nucleosome consists of which of the following components?

Accepted Answer

A histone octamer and 147 base pairs of DNA wrapped 1.7 times around it

Question 3

Which histone protein is NOT part of the nucleosome core octamer but is involved in binding linker DNA?

Accepted Answer

H1

Question 4

What is the primary function of chromatin remodeling complexes?

Accepted Answer

They use ATP hydrolysis to reposition nucleosomes, thereby regulating access to DNA.

Question 5

Which of the following histone modifications is most closely associated with active gene expression?

Accepted Answer

Acetylation of lysine residues on histone tails

Question 6

A mutation in the gene encoding MeCP2, a protein that binds methylated DNA, is most likely to affect which process?

Accepted Answer

Regulation of chromatin structure and gene silencing, as seen in Rett syndrome

Question 7

Which of the following best describes the difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is loosely packed and transcriptionally active, while heterochromatin is tightly packed and largely silent.

Question 8

Which of the following is a classic example of facultative heterochromatin?

Accepted Answer

The inactive X chromosome (Barr body) in female mammals

Question 9

What is the role of XIST RNA in X-chromosome inactivation?

Accepted Answer

It coats the X chromosome chosen for inactivation and recruits silencing enzymes.

Question 10

Which of the following best explains why calico cats are almost always female?

Accepted Answer

X-inactivation in XX females leads to a mosaic of cells expressing different X-linked coat color alleles.

Question 11

Which of the following statements about epigenetic inheritance is correct?

Accepted Answer

It involves heritable changes in gene activity without changes to the DNA sequence.

Question 12

Which of the following is the correct formula for the packing ratio of DNA in a mitotic chromosome, given that 2 meters of DNA is packed into a 1 cm chromosome?

Accepted Answer

Question 13

Which of the following best describes the function of cohesin in chromatin structure?

Accepted Answer

It forms a ring that encircles chromatin fibers at the base of looped domains, helping to organize higher-order structure.

Question 14

A researcher observes that a region of chromatin is highly compact, contains few genes, and is always silent in all cell types. This region is most likely:

Accepted Answer

Constitutive heterochromatin

Question 15

Which of the following scenarios best illustrates the concept of epigenetic inheritance?

Accepted Answer

A female mammal has two X chromosomes, but only one is active in each cell, and this pattern is passed to all daughter cells.

Question 16

Which of the following is a direct consequence of removing acetyl groups from histone H4 in a region of chromatin?

Accepted Answer

The chromatin becomes more compact and gene expression is reduced.

Question 17

A female with a mutation in one copy of the MECP2 gene may have milder symptoms of Rett syndrome if:

Accepted Answer

X-inactivation is skewed so that the mutant X is inactivated in most cells.

Question 18

Which of the following best explains why identical twins can develop different patterns of gene expression as they age?

Accepted Answer

Epigenetic changes such as histone modifications and DNA methylation can differ due to environmental influences.

Chromatin Structure and Regulation: DNA Packaging, Chromatin Remodeling, and X-Inactivation

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