Question 1

Which of the following statements best describes the structure of bacterial chromosomes?

Accepted Answer

They are circular, double-stranded DNA molecules compacted into a nucleoid with the help of nucleoid-associated proteins.

Question 2

What is the primary function of topoisomerases in both prokaryotic and eukaryotic cells?

Accepted Answer

To cut, wind, or unwind DNA strands, thereby relieving supercoiling tension.

Question 3

Which of the following best explains why supercoiling is important for viral and bacterial chromosomes?

Accepted Answer

Supercoiling facilitates the compaction of DNA, allowing it to fit within the limited space of the cell or viral capsid.

Question 4

Which of the following is a unique feature of polytene chromosomes?

Accepted Answer

They consist of paired homologs that have undergone multiple rounds of replication without strand separation or cytoplasmic division.

Question 5

What is the significance of 'puff regions' in polytene chromosomes?

Accepted Answer

They are visible manifestations of high levels of gene activity, where DNA has uncoiled for transcription.

Question 6

Which of the following statements about chromatin is correct?

Accepted Answer

Chromatin consists of DNA and proteins, primarily histones, and is dispersed throughout the nucleus during interphase.

Question 7

Which chemical modification of histones is most closely associated with increased gene activity?

Accepted Answer

Acetylation of lysine residues by histone acetyltransferase (HAT)

Question 8

What is the main difference between euchromatin and heterochromatin?

Accepted Answer

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

Question 9

Which of the following best describes the role of histones in eukaryotic chromatin?

Accepted Answer

Histones are positively charged proteins that facilitate the packaging of DNA by forming nucleosomes.

Question 10

A researcher is studying a region of DNA that is highly repetitive and found in the centromeric region of a chromosome. Which type of DNA is she most likely studying?

Accepted Answer

Satellite DNA

Question 11

Which of the following is true regarding SINEs and LINEs in the human genome?

Accepted Answer

They are transposable elements that can relocate within the genome and are dispersed throughout.

Question 12

Which enzyme is responsible for adding methyl groups to cytosine residues in DNA, and what is the typical effect of this modification?

Accepted Answer

Methyltransferase; usually decreases gene activity

Question 13

A patient is found to have a genetic disorder caused by a mutation in a region of DNA that does not encode a functional gene but resembles a known gene. What is this region called?

Accepted Answer

Pseudogene

Question 14

Which of the following best describes the process of chromatin remodeling?

Accepted Answer

The dynamic modification of chromatin structure to allow or restrict access to DNA for replication and gene expression.

Question 15

Which of the following banding techniques stains only the centromeric regions of chromosomes?

Accepted Answer

C-banding

Question 16

A forensic scientist is analyzing DNA evidence using short tandem repeats (STRs). Which category of repetitive DNA does this technique utilize?

Accepted Answer

Microsatellites

Question 17

Which of the following equations correctly represents the relationship between linking number ($$L$$), twist ($$T$$), and writhe ($$W) in $$closed-circular DNA?

Accepted Answer

$$L = T + W$$

Question 18

Which of the following is NOT a function of telomeric heterochromatin?

Accepted Answer

Encoding protein-coding genes

Question 19

Which of the following best explains why the vast majority of a eukaryotic genome does not encode functional genes?

Accepted Answer

Most of the genome consists of repetitive DNA, pseudogenes, and noncoding regions that have regulatory or unknown functions.

Question 20

Which of the following modifications to histone tails is most likely to result in chromatin condensation and gene silencing?

Accepted Answer

Methylation

DNA Organization in Chromosomes – Study Notes

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