Q: Which of the following equations correctly represents the gene product imbalance in a trisomic individual compared to a normal diploid?

$$\frac{3}{2} \times 100\% = 150\%$$

Question 1

Which of the following features is NOT typically used by cytogeneticists to identify and classify chromosomes in a karyotype?

Accepted Answer

The sequence of nucleotides

Question 2

A cytogeneticist observes a chromosome with a centromere located very close to one end, resulting in one very short arm and one very long arm. What is this chromosome type called?

Accepted Answer

Acrocentric

Question 3

G-banding is a technique used to stain chromosomes. Which of the following statements about G-banding is CORRECT?

Accepted Answer

Dark bands are AT-rich and replicate late

Question 4

Which chromosomal abnormality is responsible for cri-du-chat syndrome in humans?

Accepted Answer

Deletion on the short arm of chromosome 5

Question 5

A segment of one chromosome becomes attached to a non-homologous chromosome. If this event involves an exchange of segments between two chromosomes, what is this called?

Accepted Answer

Reciprocal translocation

Question 6

Which of the following best describes a gene family?

Accepted Answer

Two or more genes derived from the same ancestral gene

Question 7

Which of the following is a likely consequence of a pericentric inversion in a chromosome?

Accepted Answer

A segment is flipped and includes the centromere

Question 8

Familial Down syndrome is most commonly caused by which chromosomal event?

Accepted Answer

Robertsonian translocation between chromosomes 14 and 21

Question 9

Which of the following equations correctly represents the gene product imbalance in a trisomic individual compared to a normal diploid?

Accepted Answer

$$\frac{3}{2} 	imes 100\% = 150\%$$

Question 10

Which of the following statements about polyploidy in plants is TRUE?

Accepted Answer

Many agricultural crops are polyploid and display desirable traits

Question 11

A cytogeneticist observes a karyotype with 47 chromosomes, including three copies of chromosome 21. What is the most likely diagnosis?

Accepted Answer

Down syndrome (Trisomy 21)

Question 12

Which of the following mechanisms can result in mosaicism in an individual?

Accepted Answer

Mitotic nondisjunction after fertilization

Question 13

Which of the following is a plausible explanation for the increased risk of Down syndrome with advanced maternal age?

Accepted Answer

Primary oocytes are arrested in prophase I for longer periods as women age

Question 14

Which of the following best describes a copy number variation (CNV)?

Accepted Answer

A segment of DNA that varies in copy number among individuals of the same species

Question 15

Which of the following is a potential consequence of a gene being translocated from heterochromatin to euchromatin?

Accepted Answer

The gene's expression may be up-regulated

Question 16

In which of the following scenarios would you expect to see a polytene chromosome?

Accepted Answer

In the salivary glands of Drosophila

Question 17

Which of the following equations represents the expected number of chromosomes in a triploid organism if the diploid number is 24?

Accepted Answer

$$\frac{3}{2} 	imes 24 = 36$$

Question 18

Which of the following is TRUE regarding the phenotypic effects of chromosomal deletions and duplications?

Accepted Answer

Deletions are usually more detrimental than duplications of comparable size

Question 19

Which of the following is a distinguishing feature of a Robertsonian translocation?

Accepted Answer

It involves the fusion of two acrocentric chromosomes at their centromeres

Question 20

Which of the following best explains why polyploid plants are often larger and more robust than their diploid counterparts?

Accepted Answer

They have increased gene dosage, leading to enhanced cellular functions

Chromosomal Variation: Structure, Number, and Cytogenetic Analysis

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