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 cell with a karyotype of $$2n + 1$$ chromosomes is best described as:

Accepted Answer

Trisomic

Question 3

Which event most commonly leads to Down syndrome (trisomy 21) in humans?

Accepted Answer

Nondisjunction during meiosis, most often in the ovum

Question 4

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

Accepted Answer

A segment is lost from the end of the chromosome, potentially causing genetic disorders such as Cri du chat syndrome.

Question 5

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

Accepted Answer

Plants can tolerate changes in chromosome number better due to their flexible developmental processes.

Question 6

A patient is diagnosed with Fragile-X syndrome. Which genetic mechanism is most directly responsible for this condition?

Accepted Answer

A trinucleotide repeat expansion in the FMR1 gene on the X chromosome.

Question 7

Which of the following is a feature of a pericentric inversion?

Accepted Answer

The centromere is included in the inverted segment, changing the lengths of the chromosome arms.

Question 8

A plant species with a chromosome number of $$4n is $$best described as:

Accepted Answer

Tetraploid

Question 9

Which of the following is a possible outcome of a reciprocal translocation during meiosis?

Accepted Answer

Some gametes contain duplications and deficiencies, leading to semisterility.

Question 10

Gene redundancy, such as multiple copies of rRNA genes, is most often the result of which chromosomal event?

Accepted Answer

Duplication

Question 11

Which of the following best describes the genetic basis of Cri du chat syndrome?

Accepted Answer

A terminal deletion on chromosome 5

Question 12

Which process can result in the formation of an autotetraploid plant?

Accepted Answer

Chromosome doubling in a diploid cell due to colchicine treatment

Question 13

Which of the following is a likely result of nondisjunction during meiosis I?

Accepted Answer

Half the gametes are trisomic and half are monosomic.

Question 14

A compensation loop is most likely to form during meiosis in which situation?

Accepted Answer

When a chromosome has a large intercalary deletion

Question 15

Which of the following best describes allopolyploidy?

Accepted Answer

Polyploidy resulting from hybridization between two different species

Question 16

Which chromosomal aberration is most likely to result in gene dosage effects due to the presence of extra gene copies?

Accepted Answer

Duplication

Question 17

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

Accepted Answer

It contains genes that are dosage sensitive and responsible for many Down syndrome phenotypes.

Question 18

Which of the following is a characteristic of a Robertsonian translocation?

Accepted Answer

It involves the fusion of two acrocentric chromosomes, resulting in a large metacentric chromosome and loss of small segments.

Question 19

Which of the following best explains the phenomenon of genetic anticipation observed in Fragile-X syndrome?

Accepted Answer

The number of trinucleotide repeats increases with each generation, leading to earlier and more severe symptoms.

Question 20

Which of the following is a likely outcome if a crossover occurs within a paracentric inversion loop during meiosis?

Accepted Answer

One recombinant chromatid will be dicentric and another will be acentric, often leading to nonviable gametes.

Chromosome Mutations: Variation in Number and Arrangement – Study Notes

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