$$L = \frac{\text{Total number of base pairs}}{\text{Number of base pairs per turn}}$$

Question 1

Which of the following best describes the organization of DNA in prokaryotic cells?

Accepted Answer

DNA is circular, compacted in the nucleoid region, and associated with histone-like proteins such as H-NS and HU.

Question 2

What is the primary function of histone proteins in eukaryotic chromatin?

Accepted Answer

To neutralize the negative charge of DNA and facilitate its compaction.

Question 3

Which enzyme is responsible for introducing or removing supercoils in DNA?

Accepted Answer

Topoisomerase

Question 4

A nucleosome consists of which of the following components?

Accepted Answer

A histone octamer and approximately 200 base pairs of DNA

Question 5

Which chemical modification of histone tails is most likely to increase transcription by loosening chromatin structure?

Accepted Answer

Acetylation of lysine residues

Question 6

If a region of heterochromatin is translocated to a euchromatic region, what is the most likely outcome?

Accepted Answer

The region may become transcriptionally active due to the euchromatic environment.

Question 7

Which of the following best explains why histones are rich in lysine and arginine?

Accepted Answer

These amino acids are positively charged and attract the negatively charged phosphate backbone of DNA.

Question 8

Which of the following statements about polytene chromosomes is correct?

Accepted Answer

They consist of many identical DNA strands aligned in parallel, resulting from multiple rounds of replication without cell division.

Question 9

What is the effect of DNA methylation on gene expression?

Accepted Answer

It decreases gene expression by making DNA inaccessible to enzymes.

Question 10

Which of the following is a key difference between prokaryotic and eukaryotic DNA organization?

Accepted Answer

Eukaryotic DNA is associated with histones and organized into chromatin, while prokaryotic DNA is not.

Question 11

Which histone type is most lysine-rich according to the provided data?

Accepted Answer

H1

Question 12

What is the approximate length of DNA protected by a nucleosome core particle after extensive endonuclease digestion?

Accepted Answer

147 bp

Question 13

Which of the following best describes the function of H-NS and HU proteins in bacteria?

Accepted Answer

They help compact bacterial DNA by binding and folding it.

Question 14

Which equation best represents the linking number ($$L) of $$relaxed circular DNA?

Accepted Answer

$$L = \frac{	ext{Total number of base pairs}}{	ext{Number of base pairs per turn}}$$

Question 15

Which chromosomal structure is associated with increased gene expression due to its uncoiled state?

Accepted Answer

Euchromatin

Question 16

Which of the following is a consequence of histone acetylation?

Accepted Answer

Neutralization of positive charge on lysine residues, resulting in looser DNA binding and increased transcription.

Question 17

Which specialized chromosome is found in vertebrate oocytes and is associated with increased metabolic activity?

Accepted Answer

Lampbrush chromosome

Question 18

Which of the following statements about nucleosome structure is correct?

Accepted Answer

A nucleosome contains two tetramers of histones and 200 bp of DNA.

Question 19

Which of the following is true regarding the packaging of viral DNA?

Accepted Answer

Viral DNA is often much longer than the viral head and must be tightly packaged.

Question 20

Which of the following best describes the role of histone H1?

Accepted Answer

It binds to linker DNA between nucleosomes, helping to stabilize higher-order chromatin structure.

Chromosomal Organization of DNA: Structure and Function in Prokaryotes, Viruses, and Eukaryotes

Study Guide - Practice Questions