Q: If a cell contains 5 linked nucleosomes, how many base pairs of DNA are wrapped around the histone cores (excluding linker DNA)?

$$5 \times 146 = 730$$ base pairs

Question 1

Which of the following best describes the primary function of histone proteins in eukaryotic cells?

Accepted Answer

They package and organize DNA by forming nucleosomes, allowing efficient compaction within the nucleus.

Question 2

A nucleosome consists of which of the following components?

Accepted Answer

An octamer of histones (H2A, H2B, H3, H4) wrapped by approximately 146 base pairs of DNA.

Question 3

Which histone protein is responsible for binding to linker DNA and stabilizing the structure between nucleosomes?

Accepted Answer

H1

Question 4

If a genetic mutation causes the absence of histone H4 in a cell, what is the most likely consequence for chromatin structure?

Accepted Answer

Nucleosomes cannot form properly, leading to unstable chromatin and impaired DNA packaging.

Question 5

Which of the following equations correctly represents the total number of base pairs wrapped around $$n$$ nucleosomes, assuming each nucleosome core contains 146 base pairs?

Accepted Answer

$$146 	imes n$$

Question 6

In eukaryotic cells, which structure is formed when nucleosomes coil into a 30 nm fiber?

Accepted Answer

Solenoid

Question 7

A scientist observes a 'beads on a string' appearance under an electron microscope. What is being visualized?

Accepted Answer

Nucleosomes connected by linker DNA, representing chromatin in its least condensed form.

Question 8

Which of the following statements correctly distinguishes between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is loosely packed and transcriptionally active, while heterochromatin is highly condensed and inactive.

Question 9

Which of the following best describes the organization of bacterial genomes?

Accepted Answer

Circular double-stranded DNA located in the nucleoid region.

Question 10

A bacteriophage has a genome that is 17 meters long but must fit into a head less than 0.1 micrometers in diameter. Which mechanism allows this packaging?

Accepted Answer

Supercoiling and association with histone-like proteins.

Question 11

Which of the following is NOT a component of the nucleosome core?

Accepted Answer

H1

Question 12

If a cell contains 5 linked nucleosomes, how many base pairs of DNA are wrapped around the histone cores (excluding linker DNA)?

Accepted Answer

$$5 	imes 146 = 730$$ base pairs

Question 13

Which of the following best explains why histones are rich in positively charged amino acids?

Accepted Answer

To interact with the negatively charged phosphate backbone of DNA, facilitating tight binding.

Question 14

During metaphase, chromosomes are highly condensed. Which structural feature is essential for their proper segregation during cell division?

Accepted Answer

Centromere

Question 15

Which of the following is a correct sequence of chromatin organization from least to most condensed?

Accepted Answer

DNA double helix → nucleosome → 30 nm fiber (solenoid) → metaphase chromosome

Question 16

A patient has a genetic disorder resulting in unstable nucleosomes and inability to support chromatin structure. Which histones are most likely affected?

Accepted Answer

Core histones (H2A, H2B, H3, H4)

Question 17

Which equation would you use to calculate the total DNA length ($$L) in $$meters, given the number of base pairs ($$n) $$and the length per base pair ($$l) in $$meters?

Accepted Answer

$$L = n 	imes l$$

Question 18

Which of the following statements about prokaryotic and eukaryotic genome organization is correct?

Accepted Answer

Eukaryotic genomes are linear and organized into chromosomes within a nucleus, while prokaryotic genomes are circular and located in the nucleoid.

Question 19

Which of the following best describes the role of the nuclear scaffold in chromatin organization?

Accepted Answer

It provides a framework for the attachment of chromatin loops, aiding in higher-order folding.

Genome Organization: From Nucleotides to Chromosomes

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