Question 1

Which of the following best describes the molecular composition of a nucleosome?

Accepted Answer

An octamer of histones and 147 base pairs of DNA

Question 2

Why do telomeres shorten with each round of DNA replication in most human somatic cells?

Accepted Answer

DNA polymerase cannot initiate synthesis without a primer, leaving the lagging strand template incompletely replicated

Question 3

What is the function of telomerase in eukaryotic cells?

Accepted Answer

It adds repetitive DNA sequences to the ends of chromosomes, counteracting telomere shortening

Question 4

Which two primary components make up the telomerase enzyme?

Accepted Answer

TERT (Telomerase Reverse Transcriptase) and TERC (Telomerase RNA Component)

Question 5

What is the average length of linker DNA between nucleosomes in eukaryotic chromatin?

Accepted Answer

$53$ base pairs

Question 6

A mutation in the TERC gene leads to which genetic disorder, characterized by nail dystrophy, oral leukoplakia, and abnormal skin pigmentation?

Accepted Answer

Dyskeratosis congenita

Question 7

What is the main reason that the TERC+/TERC- genotype is not fully dominant to the TERC+/TERC+ genotype?

Accepted Answer

Haploinsufficiency

Question 8

Which of the following best explains the phenomenon of genetic anticipation observed in dyskeratosis congenita?

Accepted Answer

Symptoms appear at an earlier age in each generation due to inheritance of both a mutant TERC allele and shortened telomeres

Question 9

What is the role of the T-loop/D-loop structure at the ends of chromosomes?

Accepted Answer

To protect chromosome ends from being recognized as double-strand breaks by DNA repair proteins

Question 10

Which of the following is a potential risk of artificially activating telomerase in all human cells to prevent aging?

Accepted Answer

Increased risk of developing cancer due to loss of the natural limit on cell division

Question 11

In the context of nucleosome structure, which histone is associated with linker DNA?

Accepted Answer

H1

Question 12

If a human cell line is engineered to express TERT indefinitely, what is the most likely outcome?

Accepted Answer

The cells will continue dividing beyond the normal limit, potentially indefinitely

Question 13

Which equation best represents the total DNA associated with a nucleosome and its average linker DNA?

Accepted Answer

$200 = 147 + 53$

Question 14

Which of the following statements about telomerase activity in human cells is correct?

Accepted Answer

Telomerase is primarily active in germ cells, stem cells, and some immune cells

Question 15

A scientist observes that a cell line can only divide about 50 times before entering senescence. What is the most likely explanation for this observation?

Accepted Answer

The cell line experiences telomere shortening with each division, eventually losing telomere protection

Question 16

Which of the following best describes the relationship between telomere length and age in individuals with dyskeratosis congenita compared to healthy individuals?

Accepted Answer

Individuals with dyskeratosis congenita have significantly shorter telomeres at all ages compared to healthy individuals

Question 17

Which of the following is a direct consequence of losing all telomere repeats in a chromosome?

Accepted Answer

Chromosomes become unstable and cells undergo apoptosis

Question 18

What is the sequence of the telomeric repeat found in vertebrates?

Accepted Answer

$5'\ TTAGGG\ 3'$

Question 19

Which of the following best explains why the G-rich strand of the telomere forms an overhang?

Accepted Answer

The G-rich strand extends beyond the C-rich strand, allowing it to invade the duplex and form the T-loop/D-loop structure

DNA Replication in Eukaryotes: Chromatin, Telomeres, and Telomerase

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