Question 1

Which of the following best explains why genome packaging is essential in eukaryotic cells?

Accepted Answer

It solves the dimensional problem of fitting long DNA molecules into the nucleus and provides a means of organization and control over gene expression.

Question 2

Which of the following statements about euchromatin and heterochromatin is CORRECT?

Accepted Answer

Euchromatin is less densely packed and generally transcriptionally active, while heterochromatin is more condensed and mostly transcriptionally silent.

Question 3

A chromosome fragment generated by breakage that lacks a centromere is called:

Accepted Answer

Acentric fragment

Question 4

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

Accepted Answer

They protect chromosome ends from being recognized as double-strand breaks and solve the end-replication problem.

Question 5

Which enzyme is responsible for extending telomeres and what is its unique property?

Accepted Answer

Telomerase; it is an RNA-dependent DNA polymerase.

Question 6

Which of the following best describes the difference between constitutive and facultative heterochromatin?

Accepted Answer

Constitutive heterochromatin is always condensed and transcriptionally silent, while facultative heterochromatin can switch between active and inactive states depending on the cell type or developmental stage.

Question 7

A researcher observes a chromosome with two centromeres after a translocation event. What is this structure called, and what is a likely consequence during cell division?

Accepted Answer

Dicentric chromosome; it may break during anaphase due to being pulled toward opposite poles.

Question 8

Which of the following is TRUE regarding the order of genes on mitotic chromosomes compared to relaxed linear DNA?

Accepted Answer

The order of genes remains the same on mitotic chromosomes as on relaxed linear DNA.

Question 9

Which of the following best describes the role of nucleoid-associated proteins (NAPs) in bacterial chromosomes?

Accepted Answer

They compact DNA into multiple loops and affect the spatial arrangement of DNA through bending, wrapping, or bridging.

Question 10

A scientist is using Giemsa staining to analyze human chromosomes. What does a dark G-band indicate?

Accepted Answer

A region with high density of AT sequences.

Question 11

Which of the following is a key feature of polytene chromosomes that makes them useful for genetic studies?

Accepted Answer

They display puffs, which are transcriptionally active sites that can be inducible.

Question 12

Which of the following best explains why telomeres are composed of highly repetitive DNA sequences?

Accepted Answer

To allow the formation of T-loops that protect chromosome ends from degradation and fusion.

Question 13

Which of the following equations correctly represents the directionality of DNA synthesis by DNA polymerase?

Accepted Answer

$$5' \rightarrow 3'$$

Question 14

A mutation in the gene encoding the centromere-specific histone H3 (CENH3) would most likely affect which process?

Accepted Answer

Establishment of functional centromeres and proper chromosome segregation during mitosis

Question 15

Which of the following best describes the fate of telomerase activity in most human somatic cells after birth?

Accepted Answer

It is rapidly lost, leading to telomere shortening and cellular senescence.

Question 16

Which of the following is a consequence of the end-replication problem in linear chromosomes?

Accepted Answer

Chromosome ends are progressively shortened with each cell division.

Question 17

Which of the following best describes a gene family?

Accepted Answer

A set of genes with similar sequences and functions, often arising by duplication and divergence.

Question 18

Which of the following is a real-world application of microsatellite DNA?

Accepted Answer

Serving as landmarks for forensic analysis and genetic mapping.

Question 19

Which of the following best explains why chromosomes can be identified by their G-banding pattern?

Accepted Answer

Each chromosome has a unique and reproducible pattern of G-bands due to its specific sequence composition.

Question 20

Which of the following is TRUE regarding chromosome territories in the interphase nucleus?

Accepted Answer

Each chromosome occupies a distinct 3D space, and active genes from several chromosomes can cluster in interchromosomal territories enriched in transcription machinery.

Chromosome Structure and Functional Organization: Study Notes for Genetics

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