Question 1

Which of the following best describes the primary function of chromatin organization in eukaryotic cells?

Accepted Answer

To ensure proper chromosome function and distribution during cell division, and to regulate gene expression

Question 2

A nucleosome core particle consists of which combination of histone proteins?

Accepted Answer

Two molecules each of H2A, H2B, H3, and H4

Question 3

During DNA replication, what happens to the histone proteins associated with nucleosomes?

Accepted Answer

Old histones are retained as single molecules, dimers, or tetramers and are randomly distributed to daughter strands

Question 4

Which histone protein is primarily associated with stabilizing the solenoid (30-nm fiber) structure of chromatin?

Accepted Answer

H1

Question 5

If a segment of chromatin is observed to have a 'beads-on-a-string' appearance under an electron microscope, what is the diameter of this fiber and what does each 'bead' represent?

Accepted Answer

10-nm; each bead is a nucleosome

Question 6

Which of the following statements about the chromosome scaffold is correct?

Accepted Answer

It is a nonhistone protein structure that gives chromosomes their shape and anchors chromatin loops

Question 7

What is the main role of matrix attachment regions (MARS) in higher-order chromatin structure?

Accepted Answer

They anchor chromatin loops to the chromosome scaffold via nonhistone proteins

Question 8

During which phase of the cell cycle is chromatin maximally condensed, and by approximately how much is metaphase chromatin compacted compared to the 300-nm fiber?

Accepted Answer

Metaphase; 250-fold

Question 9

Which of the following best explains why eukaryotic chromosomes require compaction?

Accepted Answer

To allow the chromosomes to fit into the nucleus and to facilitate their proper segregation during cell division

Question 10

A researcher isolates chromatin and observes a 30-nm fiber under in vitro conditions. What structural feature is responsible for this observation?

Accepted Answer

The 10-nm fiber coiling into a solenoid structure stabilized by histone H1

Question 11

Which of the following statements about gene expression and chromatin loops is correct?

Accepted Answer

Larger chromatin loops tend to have more active transcription than smaller loops

Question 12

Which of the following best describes the process of nucleosome assembly after DNA replication?

Accepted Answer

Nucleosomes are assembled from a mixture of old and new histone components

Question 13

If a mutation prevents the formation of H3-H4 tetramers during nucleosome assembly, what is the most likely consequence for chromatin structure?

Accepted Answer

Nucleosome octamers will not form, preventing proper DNA compaction

Question 14

A segment of DNA wraps around a nucleosome core particle. Approximately how many base pairs are involved in this interaction?

Accepted Answer

$$\sim 146$$ base pairs

Question 15

Which of the following equations best represents the overall compaction of metaphase chromatin relative to the 300-nm fiber?

Accepted Answer

$$C_{meta} = 250 	imes C_{300}$$

Question 16

Which of the following is NOT a function of nonhistone proteins in chromatin?

Accepted Answer

Tightly binding DNA to form nucleosome core particles

Question 17

A patient is found to have a genetic defect that reduces the amount of histone H1 in their cells. Which chromatin structure is most likely to be affected?

Accepted Answer

The 30-nm solenoid fiber

Question 18

Which of the following best explains why nucleosome disassembly and reassembly are necessary during DNA replication?

Accepted Answer

To allow the replication machinery to access the DNA template

Question 19

Which of the following statements about the solenoid model of chromatin is correct?

Accepted Answer

It involves the coiling of the 10-nm fiber into a 30-nm fiber with 6-8 nucleosomes per turn

Question 20

Which of the following best describes the relationship between chromatin compaction and gene expression?

Accepted Answer

Less compacted chromatin, especially in larger loops, is associated with more active transcription

10-1. Organization of Eukaryotic Chromosomes into Chromatin

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