Question 1

Which of the following best describes the difference between euchromatin and heterochromatin in eukaryotic chromosomes?

Accepted Answer

Euchromatin is less condensed and contains more actively expressed genes than heterochromatin.

Question 2

A human cell with 47 chromosomes, including three copies of chromosome 21, is an example of which condition?

Accepted Answer

Trisomy 21

Question 3

Which technique would be most appropriate to detect a microdeletion of a specific gene on a chromosome?

Accepted Answer

Fluorescent in situ hybridization (FISH)

Question 4

A plant breeder crosses a diploid (2n) plant with a tetraploid (4n) plant. What is the expected chromosome number in the resulting triploid offspring?

Accepted Answer

$$3n$$

Question 5

Which of the following is a consequence of nondisjunction during meiosis II in a human oocyte?

Accepted Answer

Two gametes are normal, one is $$n+1$$, and one is $$n-1.$$

Question 6

Which chromosomal abnormality is associated with cri-du-chat syndrome?

Accepted Answer

Terminal deletion of chromosome 5p

Question 7

What is the primary reason that allopolyploid hybrids are often sterile before chromosome doubling?

Accepted Answer

Their chromosomes cannot pair properly during meiosis due to nonhomology.

Question 8

Which of the following best describes a Robertsonian translocation?

Accepted Answer

Fusion of two nonhomologous acrocentric chromosomes

Question 9

A chromosome inversion that does NOT include the centromere is called:

Accepted Answer

Paracentric inversion

Question 10

Which histone protein is primarily associated with stabilizing the solenoid (30-nm fiber) structure of chromatin?

Accepted Answer

H1

Question 11

A geneticist observes a Drosophila with a recessive phenotype that is normally masked by a dominant allele. Which chromosomal event could explain this observation?

Accepted Answer

Pseudodominance due to a deletion of the dominant allele

Question 12

Which of the following statements about chromosome territories is correct?

Accepted Answer

Each chromosome occupies a specific region in the nucleus called a territory during interphase.

Question 13

Which chromosomal abnormality is most commonly associated with increased maternal age?

Accepted Answer

Trisomy 21 (Down syndrome)

Question 14

Which of the following is a direct result of crossing over within a paracentric inversion loop during meiosis?

Accepted Answer

Formation of a dicentric chromosome and an acentric fragment

Question 15

Which of the following best explains why polyploid plants often have larger fruits and flowers than their diploid relatives?

Accepted Answer

Polyploidy increases gene dosage, leading to increased cell size and organ size.

Question 16

Which of the following is true regarding the composition of a nucleosome?

Accepted Answer

It contains two molecules each of H2A, H2B, H3, and H4 histones.

Question 17

A scientist observes a chromosome with a short p arm and a long q arm. What is the most likely classification of this chromosome based on centromere position?

Accepted Answer

Submetacentric

Question 18

Which of the following best describes position effect variegation (PEV) in Drosophila?

Accepted Answer

It results from changes in chromatin structure that affect gene expression.

Question 19

Which of the following is a likely outcome if a chromosome fragment lacking a centromere (acentric) is generated during cell division?

Accepted Answer

The fragment will be lost during cell division.

Question 20

Which of the following best explains the concept of uniparental disomy?

Accepted Answer

Both copies of a chromosome pair are inherited from one parent.

Eukaryotic Chromosome Abnormalities and Molecular Organization: Study Guide

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