Question 1

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

Accepted Answer

Aneuploidy refers to a change in the number of individual chromosomes, while euploidy refers to a change in the number of complete chromosome sets.

Question 2

A human karyotype shows 47 chromosomes with three copies of chromosome 21. What is the genetic condition called, and what is the chromosomal formula?

Accepted Answer

Down syndrome; $$2n+1$$

Question 3

Which mechanism most commonly leads to the formation of triploid bananas and seedless watermelons?

Accepted Answer

Autopolyploidy due to meiotic nondisjunction

Question 4

What is the primary cause of the increased risk of Down syndrome with advancing maternal age, as shown in the provided graph?

Accepted Answer

Increased rate of meiotic nondisjunction in oocytes

Question 5

A karyotype analysis reveals a female with 45 chromosomes, including only one X chromosome and no second sex chromosome. Which syndrome does this describe, and what is a common phenotype?

Accepted Answer

Turner syndrome; short stature and webbed neck

Question 6

Which of the following is a likely consequence of a Robertsonian translocation between two acrocentric chromosomes?

Accepted Answer

Decrease in chromosome number by one

Question 7

What is the genetic basis for the bilateral split of male and female characteristics in some insects, such as the butterfly shown in the images?

Accepted Answer

Sex-chromosome mosaicism due to mitotic nondisjunction

Question 8

Which of the following best explains why plants tolerate aneuploidy better than animals?

Accepted Answer

Plants can often survive with altered gene dosage due to their developmental plasticity.

Question 9

A partial chromosome deletion that removes the end of a chromosome arm is called a:

Accepted Answer

Terminal deletion

Question 10

Which of the following is a direct evolutionary consequence of gene duplication?

Accepted Answer

Formation of pseudogenes due to loss of function in duplicate copies

Question 11

Which of the following statements about G-banding is correct?

Accepted Answer

G-banding produces consistent banding patterns that can be used to identify chromosomal abnormalities.

Question 12

Which of the following is a characteristic of Class I transposable elements (retrotransposons)?

Accepted Answer

They move via an RNA intermediate and increase in copy number.

Question 13

A maize kernel is yellow due to the insertion of a Ds element in the C gene. What would cause the appearance of purple spots on this kernel?

Accepted Answer

Excision of the Ds element by Ac-activated transposase

Question 14

Which of the following is true about allopolyploidy in plants?

Accepted Answer

It often leads to the formation of new species through hybridization and chromosome doubling.

Question 15

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

Accepted Answer

Formation of a tetravalent complex and semi-sterility of gametes.

Question 16

Which of the following best describes the effect of an extra chromosome on gene dosage?

Accepted Answer

Gene products are produced at 150% of the normal concentration.

Question 17

Which of the following is a feature of composite transposons in bacteria?

Accepted Answer

They contain two insertion sequences flanking one or more genes, often including antibiotic resistance genes.

Question 18

What is the most likely explanation for the presence of both male and female characteristics in a single cardinal bird, as shown in the images?

Accepted Answer

Gynandromorphism resulting from sex-chromosome mosaicism

Question 19

Which of the following is a possible evolutionary fate of a duplicated gene?

Accepted Answer

It may become a pseudogene due to loss of function.

Chromosome Aberrations and Transposition: Study Notes for Genetics Students

Study Guide - Practice Questions

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