Question 1

Which of the following best describes aneuploidy?

Accepted Answer

A condition in which an organism gains or loses one or more individual chromosomes, but not a complete set.

Question 2

A human karyotype shows 47 chromosomes, with three copies of chromosome 21. What is the most likely diagnosis?

Accepted Answer

Down syndrome

Question 3

Which process most commonly leads to the formation of gametes with an abnormal number of chromosomes?

Accepted Answer

Nondisjunction during meiosis

Question 4

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

Accepted Answer

$$21$$

Question 5

Which of the following is a likely consequence of monosomy in humans?

Accepted Answer

Unmasking of recessive lethal alleles, leading to nonviability

Question 6

What is the most common source of the extra chromosome in Down syndrome?

Accepted Answer

Nondisjunction during oogenesis

Question 7

Which of the following best describes an allopolyploid?

Accepted Answer

An organism with chromosome sets derived from different species

Question 8

A chromosomal rearrangement that results in a segment of a chromosome being reversed end to end is called:

Accepted Answer

Inversion

Question 9

Which of the following is true about paracentric inversions?

Accepted Answer

They do not change the lengths of the chromosome arms.

Question 10

A child is diagnosed with Cri du chat syndrome. Which chromosomal abnormality is most likely responsible?

Accepted Answer

A terminal deletion on chromosome 5

Question 11

Which of the following mechanisms can lead to gene duplication?

Accepted Answer

Unequal crossing over during meiosis

Question 12

Which chromosomal rearrangement is most likely to result in semisterility due to the production of gametes with duplications and deficiencies?

Accepted Answer

Reciprocal translocation

Question 13

A plant breeder treats a diploid plant with colchicine, resulting in a tetraploid plant. What is the chromosome number of the tetraploid if the diploid number is 18?

Accepted Answer

$$36$$

Question 14

Which of the following is a feature of fragile sites on human chromosomes?

Accepted Answer

They are more susceptible to breakage in the absence of folic acid.

Question 15

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 number and still remain viable.

Question 16

A person with Fragile-X syndrome is found to have over 230 trinucleotide repeats in the FMR1 gene. What genetic phenomenon does this illustrate?

Accepted Answer

Genetic anticipation

Question 17

Which of the following is a likely outcome of a pericentric inversion crossover during meiosis?

Accepted Answer

Recombinant chromatids with duplications and deletions

Question 18

A Robertsonian translocation involves which of the following?

Accepted Answer

Fusion of the long arms of two acrocentric chromosomes with loss of short arms

Question 19

Which of the following best describes haploinsufficiency?

Accepted Answer

A condition where one copy of a gene is not sufficient for normal function

Question 20

Which of the following is an example of gene redundancy?

Accepted Answer

Multiple copies of rRNA genes in the genome

Chromosome Mutations: Variation in Number and Arrangement

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