Question 1

A human karyotype shows three copies of chromosome 21. Which condition does this represent, and what is the chromosome number in such an individual?

Accepted Answer

Trisomy 21; 47 chromosomes

Question 2

Which of the following best describes the difference between aneuploidy and euploidy?

Accepted Answer

Aneuploidy involves the loss or gain of individual chromosomes, while euploidy involves changes in the number of complete chromosome sets.

Question 3

A plant species has a diploid number of 14. A tetraploid individual of this species would have how many chromosomes?

Accepted Answer

$$4n = 28$$

Question 4

Which of the following is a likely consequence of nondisjunction during meiosis II?

Accepted Answer

Half the gametes will be normal, and half will be aneuploid.

Question 5

A child is born with Turner syndrome. Which of the following karyotypes is consistent with this diagnosis?

Accepted Answer

45, XO

Question 6

Which of the following best explains why most autosomal monosomies are not observed in live births?

Accepted Answer

Monosomic gametes are functionally impaired and often do not result in viable embryos.

Question 7

Which of the following is an example of allopolyploidy in agriculture?

Accepted Answer

American cotton, which is a fertile amphidiploid derived from Old World and wild American cotton species

Question 8

A chromosome undergoes two breaks and the segment between the breaks is reinserted in the opposite orientation. What type of chromosomal mutation is this?

Accepted Answer

Inversion

Question 9

Which of the following chromosomal rearrangements is most likely to result in a compensation loop during meiosis?

Accepted Answer

Intercalary deletion

Question 10

A karyotype shows 2n = 63 chromosomes in a mule. What is the best explanation for this chromosome number?

Accepted Answer

The mule is aneuploid, resulting from a cross between a horse (2n = 64) and a donkey (2n = 62).

Question 11

Which of the following best describes a reciprocal translocation?

Accepted Answer

Segments are exchanged between two nonhomologous chromosomes.

Question 12

Cri du Chat syndrome is caused by which chromosomal event?

Accepted Answer

A terminal deletion on chromosome 5

Question 13

Which of the following formulas correctly represents a trisomic individual?

Accepted Answer

$$2n + 1$$

Question 14

A plant cell fails to divide after chromosome replication, resulting in a tetraploid cell. What is this process called?

Accepted Answer

Autopolyploidy

Question 15

Which of the following is a likely outcome of a pericentric inversion?

Accepted Answer

The arm ratio of the chromosome changes.

Question 16

A chromosome mutation results in the gain of a segment from a nonhomologous chromosome. What is this called?

Accepted Answer

Nonreciprocal translocation

Question 17

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

Accepted Answer

Plants can often tolerate changes in chromosome set number and may even benefit from increased genetic diversity.

Question 18

Which of the following is a possible result of unequal crossing over during meiosis?

Accepted Answer

Duplication

Question 19

A chromosome with a large intercalary deletion pairs with its normal homolog during meiosis. What structure is likely to form?

Accepted Answer

A deletion (compensation) loop

Question 20

Which of the following best describes haploinsufficiency?

Accepted Answer

A single functional copy of a gene is not sufficient for normal function.

Chromosome Mutations: Variation in Chromosome Number and Arrangement

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