Question 1

Which of the following best describes aneuploidy?

Accepted Answer

A condition in which an organism has one or more extra or missing chromosomes, but not a complete set.

Question 2

A human cell with a karyotype of $$47, 21+ is $$best described as:

Accepted Answer

Aneuploid, specifically trisomy 21 (Down syndrome)

Question 3

Which of the following is a likely consequence of a terminal deletion on a chromosome?

Accepted Answer

Loss of genetic material from the end of the chromosome, potentially resulting in severe phenotypic effects

Question 4

Which process most commonly leads to the formation of Down syndrome?

Accepted Answer

Nondisjunction of chromosome 21 during meiosis, resulting in a gamete with two copies of chromosome 21

Question 5

Which of the following best explains why polyploidy is more common in plants than in animals?

Accepted Answer

Plants can often tolerate and propagate polyploid cells, while animals usually cannot survive such changes.

Question 6

A child is born with cri du chat syndrome. Which chromosomal event is responsible for this condition?

Accepted Answer

A segmental deletion of the short arm of chromosome 5

Question 7

Which of the following is a possible outcome of a single crossover within a paracentric inversion loop during meiosis?

Accepted Answer

Production of one dicentric chromatid and one acentric chromatid, both with duplications and deletions

Question 8

Which of the following statements about gene duplication is correct?

Accepted Answer

Gene duplication can provide raw material for evolutionary innovation by allowing one copy to acquire new functions.

Question 9

A plant species is found to have 3n chromosomes. Which term best describes this condition?

Accepted Answer

Triploidy

Question 10

Which of the following mechanisms can result in an autotriploid plant?

Accepted Answer

Fertilization of a diploid gamete with a haploid gamete

Question 11

Which chromosomal aberration is most likely to result in a compensation loop during meiosis?

Accepted Answer

Intercalary deletion

Question 12

A reciprocal translocation between two nonhomologous chromosomes will most likely result in which of the following during meiosis?

Accepted Answer

Production of both balanced and unbalanced gametes, depending on the segregation pattern

Question 13

Which of the following is a real-world example of a disease caused by a segmental deletion?

Accepted Answer

Cri du chat syndrome

Question 14

Which of the following best describes the effect of colchicine on dividing cells?

Accepted Answer

It prevents spindle formation, leading to chromosome doubling and polyploidy.

Question 15

Which of the following is true regarding the Down syndrome critical region (DSCR) on chromosome 21?

Accepted Answer

It contains dosage-sensitive genes responsible for many Down syndrome phenotypes.

Question 16

Which of the following is a likely evolutionary advantage of chromosomal inversions?

Accepted Answer

They can preserve beneficial allele combinations by suppressing recombination.

Question 17

Which of the following best explains why monosomy for an autosome is usually lethal in humans?

Accepted Answer

Haploinsufficiency: a single copy of essential genes is not sufficient for survival.

Question 18

Which of the following is a characteristic feature of fragile-X syndrome?

Accepted Answer

A folate-sensitive site on the X chromosome associated with intellectual disability.

Question 19

Which of the following best describes a multigene family?

Accepted Answer

A group of contiguous genes with similar functions that arose from gene duplication.

Question 20

Which of the following is a possible outcome of adjacent segregation in a translocation heterozygote?

Accepted Answer

Gametes with duplications and deficiencies, leading to unbalanced genetic content.

Chromosome Mutations: Variation in Number and Arrangement

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