Q: Which equation best represents the compaction of DNA by nucleosomes?

$$\text{Compaction factor} = 7$$

Question 1

Which of the following best describes the function of histone H1 in the nucleosome?

Accepted Answer

It locks DNA into place around the histone core, stabilizing the nucleosome structure.

Question 2

A human cell contains approximately 6 billion base pairs of DNA. If the DNA were stretched out, it would be about 2 meters long. What is the primary reason this DNA can fit inside the nucleus?

Accepted Answer

DNA is compacted by winding around histone proteins to form chromatin.

Question 3

Which histone modification is most likely to result in gene expression in euchromatin?

Accepted Answer

Acetylation of histone tails

Question 4

What is the effect of histone acetyltransferases (HAT) on chromatin structure?

Accepted Answer

They add acetyl groups to histone tails, neutralizing positive charges and loosening chromatin.

Question 5

Which equation best represents the compaction of DNA by nucleosomes?

Accepted Answer

$$	ext{Compaction factor} = 7$$

Question 6

During DNA replication, nucleosomes are disassembled and reformed. Which histones are first to associate with newly synthesized DNA?

Accepted Answer

A tetramer of H3 and H4

Question 7

Which of the following is a characteristic of heterochromatin?

Accepted Answer

It is highly compact and genes are silenced.

Question 8

What is the primary function of telomeres in eukaryotic chromosomes?

Accepted Answer

To protect chromosome ends from degradation and fusion.

Question 9

Which enzyme is responsible for extending telomeric repeats in certain cell types?

Accepted Answer

Telomerase

Question 10

In higher eukaryotes, centromeres are composed of:

Accepted Answer

Tandem repeats of non-coding satellite DNAs

Question 11

Which histone protein replaces H3 at centromeres to scaffold kinetochore protein binding?

Accepted Answer

CENP-A

Question 12

Which of the following statements about bacterial chromosomes is correct?

Accepted Answer

Bacteria usually have a single circular chromosome condensed by supercoiling.

Question 13

If a gene is silenced due to the spreading of heterochromatin, which histone modification is most likely involved?

Accepted Answer

Methylation of H3 lysine 9

Question 14

Which of the following best explains why most mammalian genomes have multiple origins of replication?

Accepted Answer

To ensure that DNA replication occurs quickly enough to complete cell division.

Question 15

Which protein complex binds to telomeres to protect them from nuclease degradation and non-homologous end joining (NHEJ)?

Accepted Answer

Shelterin

Question 16

Which equation describes the number of chromosomes in a diploid human cell?

Accepted Answer

$$2n = 46$$

Question 17

Which of the following is NOT a function of non-histone scaffold proteins in chromatin?

Accepted Answer

Forming the core of the nucleosome

Question 18

Which equation best represents the relationship between the number of origins of replication and the time required to replicate the human genome?

Accepted Answer

$$	ext{Time} = \frac{	ext{Genome size}}{	ext{Replication rate} 	imes 	ext{Number of origins}}$$

Question 19

Which of the following best describes the radial loop-scaffold model of chromosome compaction?

Accepted Answer

Chromatin loops are tethered by scaffold proteins and further compacted into rosettes.

Question 20

Which equation best represents the length of DNA after nucleosome compaction, given an initial length of $$L$$?

Accepted Answer

$$L_{	ext{compacted}} = \frac{L}{7}$$

DNA Organization in Chromosomes: Structure, Compaction, and Functional Implications

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