Question 1

Which of the following statements best explains why two closely related salamander species can have a two-fold difference in genome size?

Accepted Answer

The difference is primarily due to the presence of more repetitive DNA sequences in one species.

Question 2

Which of the following is NOT a function of the centromere in eukaryotic chromosomes?

Accepted Answer

It serves as the primary site for DNA replication initiation.

Question 3

A researcher is studying a eukaryotic chromosome and finds a region that is highly condensed, transcriptionally inactive, and inaccessible to most proteins. This region is best described as:

Accepted Answer

Heterochromatin

Question 4

Which of the following best describes the structure of a nucleosome?

Accepted Answer

A segment of DNA wrapped around a histone octamer, consisting of two copies each of H2A, H2B, H3, and H4.

Question 5

Which of the following equations correctly represents the compaction levels leading to a metaphase chromosome, from least to most compact?

Accepted Answer

$$2\ \mathrm{nm} \rightarrow 11\ \mathrm{nm} \rightarrow 30\ \mathrm{nm} \rightarrow 300\ \mathrm{nm} \rightarrow 700\ \mathrm{nm} \rightarrow 1400\ \mathrm{nm}$$

Question 6

Which of the following is a key difference between the genomes of lower eukaryotes (such as yeast) and higher eukaryotes (such as mammals)?

Accepted Answer

Higher eukaryotes have longer introns and more non-coding DNA.

Question 7

A mutation in the cohesin complex can lead to Cornelia de Lange Syndrome (CdLS). Which of the following best explains the molecular basis for this disorder?

Accepted Answer

Cohesin mutations disrupt the alignment of sister chromatids and alter gene transcription by affecting chromatin structure.

Question 8

Which of the following statements about repetitive DNA sequences is TRUE?

Accepted Answer

Moderately repetitive sequences include genes for rRNA and histones.

Question 9

In eukaryotic chromosomes, what is the primary role of telomeres?

Accepted Answer

To contain specialized sequences that protect chromosome ends from degradation.

Question 10

Which of the following best describes the function of condensin during mitosis?

Accepted Answer

Condensin is critical for chromosome condensation by compacting radial loops into a metaphase chromosome.

Question 11

A scientist is comparing the genomes of two eukaryotic species. Species A has a genome size of $$10^9$$ base pairs, while species B has a genome size of $$10^{10}$$ base pairs. Which of the following is the most likely explanation for the difference in genome size?

Accepted Answer

Species B has a greater amount of repetitive DNA sequences.

Question 12

Which of the following statements about the organization of bacterial chromosomes is CORRECT?

Accepted Answer

Bacterial chromosomes are circular and located in the nucleoid region.

Question 13

Which of the following best describes the role of the nuclear matrix in eukaryotic chromosome organization?

Accepted Answer

It provides attachment sites (MARS) for radial loop domains, contributing to higher-order chromatin structure.

Question 14

Which of the following is a characteristic of euchromatin?

Accepted Answer

It is less condensed and transcriptionally active.

Question 15

Which of the following best explains why genome size does not correlate with organismal complexity in eukaryotes?

Accepted Answer

Variation in genome size is largely due to differences in the amount of repetitive DNA, not the number of genes.

Question 16

Which of the following is TRUE regarding the number and distribution of origins of replication in eukaryotic chromosomes?

Accepted Answer

Origins of replication are interspersed about every 100,000 base pairs along each chromosome.

Question 17

A mutation eliminates the linker histone H1 in a eukaryotic cell. Which of the following is the most likely consequence?

Accepted Answer

The 30 nm fiber will be less stable, leading to reduced chromatin compaction.

Question 18

Which of the following best describes the function of SMC (Structural Maintenance of Chromosomes) proteins?

Accepted Answer

They use ATP to catalyze changes in chromosome structure, as part of cohesin and condensin complexes.

Question 19

Which of the following is a feature of bacterial chromosome organization that distinguishes it from eukaryotic chromosomes?

Accepted Answer

Bacterial chromosomes are organized into micro-domains and are not enclosed by a nuclear membrane.

Chromosome Organization: Structure and Function in Genetics

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