Question 1

Which of the following statements best describes the difference between B-DNA and Z-DNA as shown in the provided image?

Accepted Answer

B-DNA is the most common form in cells, while Z-DNA is a left-handed helix found in synthetic DNA with only G-C pairs.

Question 2

A DNA molecule is 300 base pairs long and has 20 complete rotations. Is this DNA molecule supercoiled, and if so, in which direction?

Accepted Answer

It is negatively supercoiled.

Question 3

Which enzyme is responsible for introducing or removing supercoils in DNA by cleaving one or both DNA strands?

Accepted Answer

Topoisomerase

Question 4

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

Accepted Answer

To neutralize the negative charge of DNA and facilitate its compaction

Question 5

If a chemist develops a drug that neutralizes the positive charges on histone tails, what is the most likely effect on chromatin structure?

Accepted Answer

Chromatin would become less condensed, increasing gene expression.

Question 6

Which of the following is a characteristic of viral chromosomes?

Accepted Answer

They can be DNA or RNA, single or double stranded, and circular or linear.

Question 7

Which histone is NOT part of the nucleosome core but is involved in higher-order chromatin structure?

Accepted Answer

H1

Question 8

How many copies of the H2B histone would be found in chromatin containing 50 nucleosomes?

Accepted Answer

100

Question 9

Which chemical modification of histone tails is most directly linked to gene activation?

Accepted Answer

Acetylation

Question 10

A diploid plant cell contains $$2 	imes 10^9$ base pairs of DNA. If each nucleosome contains 147 base pairs, approximately how many nucleosomes are present in the cell?

Accepted Answer

$$1.36 	imes 10^7$

Question 11

Which of the following best describes the difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is uncoiled and active, while heterochromatin is condensed and inactive.

Question 12

Which of the following DNA forms is left-handed and typically found in synthetic DNA oligonucleotides containing only G-C pairs?

Accepted Answer

Z-DNA

Question 13

Which of the following is a function of the centromere in eukaryotic chromosomes?

Accepted Answer

Facilitating chromosome movement during cell division

Question 14

Which of the following repetitive DNA elements is most commonly found in the human genome as a short tandem repeat (STR)?

Accepted Answer

(CA)n

Question 15

Which of the following best explains why topoisomerase II is essential during DNA replication?

Accepted Answer

It cleaves both DNA strands to relieve supercoiling and untangle DNA.

Question 16

Which of the following is true about the proportion of the human genome that encodes functional genes?

Accepted Answer

About 2% encodes functional genes.

Question 17

Which of the following is a main component of centromeres and consists of short sequences repeated numerous times in tandem?

Accepted Answer

Satellite DNA

Question 18

What is the effect of acetylation of lysine residues on histone tails?

Accepted Answer

It neutralizes the positive charge, loosening DNA binding.

Question 19

Which of the following best describes the role of HU and H-NS proteins in bacterial chromosomes?

Accepted Answer

They fold and bend DNA to compact it into the nucleoid.

Question 20

Which of the following is a characteristic of pseudogenes?

Accepted Answer

They are evolutionary vestiges of duplicated genes with mutational alterations.

DNA Organization in Chromosomes: Structure, Packing, and Chromatin Remodeling

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