Question 1

Which protein is primarily responsible for compacting bacterial DNA into the nucleoid region, and what is its mechanism of action?

Accepted Answer

H-NS, which binds to DNA via positively charged residues and folds it

Question 2

In eukaryotic chromatin, what is the composition of a nucleosome core particle?

Accepted Answer

Two tetramers: H2A-H2B and H3-H4, wrapped by 147 bp of DNA

Question 3

Which chemical modification of histone tails is most likely to increase transcription by neutralizing positive charges on lysine residues?

Accepted Answer

Acetylation

Question 4

A relaxed circular DNA molecule has a linking number $$L = 20. $$After underwinding by two turns, what is the new linking number?

Accepted Answer

$$L = 18$$

Question 5

Which of the following best describes the function of histone H1 in chromatin structure?

Accepted Answer

It binds to linker DNA between nucleosomes, stabilizing higher-order structure

Question 6

Polytene chromosomes are characterized by which of the following features?

Accepted Answer

Presence of many identical DNA strands aligned in parallel, forming visible bands

Question 7

What is the primary reason that histones are rich in lysine and arginine?

Accepted Answer

To neutralize the phosphate backbone of DNA via positive charges

Question 8

Which enzyme is responsible for introducing supercoiling into DNA molecules?

Accepted Answer

Topoisomerase

Question 9

If a region of heterochromatin is translocated to a euchromatic region, what is the most likely effect on gene expression?

Accepted Answer

Genes in the translocated region become more accessible and may be expressed

Question 10

Which of the following statements about lampbrush chromosomes is correct?

Accepted Answer

They are meiotic chromosomes with extended loops for increased transcription

Question 11

Which form of chromatin is most likely to be actively transcribed?

Accepted Answer

Euchromatin

Question 12

What is the effect of DNA methylation on gene expression?

Accepted Answer

It makes DNA inaccessible to enzymes, leading to loss of function

Question 13

Which of the following best explains why eukaryotic chromosomes can fit into a small nucleus despite their length?

Accepted Answer

DNA is compacted by wrapping around histones and further coiling into chromatin fibers

Question 14

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

Accepted Answer

H1

Question 15

Which of the following is a plausible consequence of histone acetylation?

Accepted Answer

Chromatin structure loosens, increasing transcription

Question 16

Which of the following is NOT a feature of prokaryotic chromosomes?

Accepted Answer

Multiple linear chromosomes

Question 17

Which of the following best describes the 'beads on a string' pattern observed in chromatin?

Accepted Answer

Nucleosomes spaced along DNA, each consisting of histone octamers and wrapped DNA

Question 18

Which protein modification is most likely to cause a negative charge on histone tails?

Accepted Answer

Phosphorylation

Question 19

Which chromosome structure is associated with increased gene expression due to areas of uncoiling called 'puffs'?

Accepted Answer

Polytene chromosomes

Question 20

Which of the following is a unique feature of eukaryotic chromosomes compared to prokaryotic chromosomes?

Accepted Answer

Presence of histones and nucleosomes

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

Study Guide - Practice Questions