Question 1

Which of the following best explains why Thomas Hunt Morgan chose Drosophila melanogaster (fruit flies) for his genetic experiments?

Accepted Answer

They have a short generation time and only four pairs of chromosomes, making them ideal for genetic studies.

Question 2

Morgan’s experiments with fruit flies provided evidence for which of the following theories?

Accepted Answer

The chromosome theory of inheritance

Question 3

In Morgan’s cross between white-eyed male and red-eyed female fruit flies, all F1 offspring had red eyes. In the F2 generation, only males had white eyes. What does this pattern suggest?

Accepted Answer

The white-eye allele is recessive and located on the X chromosome.

Question 4

Which of the following statements about X-linked recessive disorders is correct?

Accepted Answer

A male needs only one copy of the allele to express the disorder.

Question 5

A woman who is heterozygous for an X-linked gene will be a mosaic for that character because:

Accepted Answer

One X chromosome is randomly inactivated in each cell during embryonic development.

Question 6

Which gene is responsible for X chromosome inactivation in female mammals?

Accepted Answer

XIST

Question 7

Linked genes tend to be inherited together because:

Accepted Answer

They are located near each other on the same chromosome.

Question 8

If two genes are 17 map units apart, what is the expected recombination frequency between them?

Accepted Answer

$$17\%$$

Question 9

Which chromosomal alteration is correctly matched with its description?

Accepted Answer

Inversion: Reverses orientation of a segment within a chromosome

Question 10

A child is born with three copies of chromosome 21. This condition is known as:

Accepted Answer

Down syndrome

Question 11

A geneticist observes that two genes have a recombination frequency of nearly $$50\%. $$What does this suggest about the genes?

Accepted Answer

They are on different chromosomes or far apart on the same chromosome.

Question 12

Which of the following is an example of a disorder caused by a chromosomal translocation?

Accepted Answer

Chronic myelogenous leukemia (CML)

Question 13

Which of the following best describes genomic imprinting?

Accepted Answer

It is the silencing of certain genes depending on which parent passes them on.

Question 14

A woman with mitochondrial myopathy is concerned about passing the disorder to her children. Which statement is correct?

Accepted Answer

All of her children can inherit the disorder because mitochondria are maternally inherited.

Question 15

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

Accepted Answer

Plants tolerate extra sets of chromosomes better than animals.

Question 16

A male with an extra X chromosome (XXY) has which syndrome?

Accepted Answer

Klinefelter syndrome

Question 17

Which process is responsible for the production of recombinant chromosomes during meiosis?

Accepted Answer

Crossing over

Question 18

If a female is heterozygous for a recessive X-linked disorder and her partner is unaffected, what is the probability that their son will have the disorder?

Accepted Answer

$$0.25$$

Question 19

Which of the following is true about extranuclear (cytoplasmic) inheritance?

Accepted Answer

It is inherited from the mother only.

Question 20

A plant geneticist observes a leaf with both green and white patches. This is most likely due to:

Accepted Answer

A mutation in the chloroplast DNA, inherited maternally.

The Chromosomal Basis of Inheritance

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