Question 1

Which of the following best describes the role of histone acetylation in chromatin structure and gene expression?

Accepted Answer

Histone acetylation decreases the overall positive charge of histones, allowing DNA to loosely coil and promoting gene expression.

Question 2

What is the primary function of telomeres in eukaryotic chromosomes?

Accepted Answer

To protect chromosome ends from degradation and prevent loss of genetic information during DNA replication.

Question 3

During DNA replication, why is the lagging strand synthesized in fragments known as Okazaki fragments?

Accepted Answer

Because DNA polymerase can only synthesize DNA in the 5' to 3' direction, requiring discontinuous synthesis as the replication fork opens.

Question 4

Which chemical modification of histones is most commonly associated with transcriptionally inactive heterochromatin?

Accepted Answer

Histone methylation

Question 5

A cell is observed to have highly condensed chromatin that is inaccessible to RNA polymerase. Which term best describes this chromatin state?

Accepted Answer

Heterochromatin

Question 6

Which of the following best explains why eukaryotic chromosomes require telomerase activity in certain cell types?

Accepted Answer

Telomerase adds repetitive sequences to chromosome ends, compensating for incomplete replication of the lagging strand.

Question 7

If a mutation prevents the acetylation of histone proteins, what is the most likely effect on gene expression?

Accepted Answer

Gene expression will decrease due to tighter chromatin structure.

Question 8

Which formula correctly represents the number of possible chromosome combinations in human gametes due to independent assortment?

Accepted Answer

$2^{23}$

Question 9

A researcher treats cells with a drug that inhibits histone methyltransferase. What is the most likely outcome regarding chromatin structure and gene expression?

Accepted Answer

Chromatin will become less condensed and gene expression will increase.

Question 10

Which of the following statements about nucleosomes is correct?

Accepted Answer

Nucleosomes consist of DNA wrapped around a core of eight histone proteins.

Question 11

Which process is responsible for the inability of DNA polymerase to fully replicate the ends of linear chromosomes?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, leaving a gap at the 3' end of the lagging strand.

Question 12

Which of the following best describes euchromatin?

Accepted Answer

Euchromatin is loosely packed and transcriptionally active.

Question 13

A cell line is found to have abnormally short telomeres after several rounds of division. Which of the following is the most likely consequence?

Accepted Answer

Decreased chromosomal integrity and increased risk of genetic information loss.

Question 14

Which of the following is NOT a function of histone proteins in eukaryotic cells?

Accepted Answer

Serving as enzymes for DNA replication.

Question 15

Which of the following sequences is most likely to be found at the end of a human chromosome?

Accepted Answer

$TTAGGG$

Question 16

Which of the following best explains why heterochromatin is transcriptionally inactive?

Accepted Answer

Heterochromatin is highly condensed, making DNA inaccessible to polymerases.

Question 17

A scientist observes that a certain gene is silenced in a cell. Which epigenetic modification is most likely responsible for this silencing?

Accepted Answer

DNA methylation

Question 18

Which of the following statements about the origin of replication in eukaryotic DNA is correct?

Accepted Answer

Multiple origins of replication allow for faster and more efficient DNA replication.

Question 19

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Homologous chromosomes contain the same genes but may have different alleles, while sister chromatids are identical copies formed during DNA replication.

Question 20

A tumor cell is found to have high telomerase activity. What is the most likely effect of this on the cell?

Accepted Answer

The cell will maintain telomere length, allowing for continuous replication and potential immortality.

DNA Condensation into Chromosomes: Mechanisms and Biological Significance

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