Question 1

Which statement best describes the chromosome theory of inheritance?

Accepted Answer

Mendelian genes have specific loci on chromosomes, and chromosomes undergo segregation and independent assortment during meiosis.

Question 2

In Thomas Hunt Morgan's experiments with Drosophila melanogaster, what was the significance of discovering a white-eyed mutant fly?

Accepted Answer

It provided the first solid evidence that a specific gene is located on a specific chromosome.

Question 3

Which of the following best explains why fruit flies (Drosophila melanogaster) are a convenient organism for genetic studies?

Accepted Answer

They have only four pairs of chromosomes and produce many offspring in a short time.

Question 4

In Morgan's cross between a wild-type female fruit fly and a mutant white-eyed male, what was the eye color of all F1 offspring?

Accepted Answer

All had red eyes.

Question 5

Which of the following is true regarding sex-linked genes?

Accepted Answer

Sex-linked genes are located on either the X or Y chromosome.

Question 6

A woman who is a carrier for red-green color blindness (an X-linked recessive trait) and a man with normal vision have a child. What is the probability that their son will be colorblind?

Accepted Answer

$$0.50$$

Question 7

Why are X-linked recessive disorders more common in males than in females?

Accepted Answer

Males are hemizygous for the X chromosome, so a single recessive allele will cause the disorder.

Question 8

What is the function of X inactivation in female mammals?

Accepted Answer

To prevent double dosing of gene products from the X chromosome by randomly inactivating one X in each cell.

Question 9

Which of the following best describes a Barr body?

Accepted Answer

A condensed, inactivated X chromosome in female mammals.

Question 10

If a female cat is heterozygous for fur color genes on the X chromosome, what is the expected result due to X inactivation?

Accepted Answer

Some cells will express one allele, and other cells will express the other allele, resulting in a mosaic fur pattern.

Question 11

Which of the following is true about linked genes?

Accepted Answer

Linked genes are located near each other on the same chromosome and tend to be inherited together.

Question 12

What is the most likely outcome if a crossover event occurs between two genes that are very close together on the same chromosome?

Accepted Answer

The genes are less likely to be separated by crossing over and will usually be inherited together.

Question 13

Which chromosomal abnormality results from nondisjunction during meiosis?

Accepted Answer

Aneuploidy, such as trisomy 21 (Down syndrome)

Question 14

A zygote with only one copy of a particular chromosome is called:

Accepted Answer

Monosomic

Question 15

Which of the following chromosomal conditions is associated with Klinefelter syndrome?

Accepted Answer

XXY

Question 16

Which type of chromosomal structural alteration involves the removal of a chromosomal segment?

Accepted Answer

Deletion

Question 17

A plant species is found to have three complete sets of chromosomes in each cell. What is this condition called?

Accepted Answer

Triploidy ($$3n)$$

Question 18

Which of the following best explains why plants can often tolerate polyploidy better than animals?

Accepted Answer

Plants can survive and reproduce with multiple sets of chromosomes, while animals usually cannot.

Question 19

Which chromosomal structural alteration is most likely to cause reproductive problems due to altered gene expression, even if the balance of genes remains normal?

Accepted Answer

Inversion

Question 20

A male with the genotype XYY is most likely to have which of the following conditions?

Accepted Answer

Jacobs syndrome

The Chromosomal Basis of Inheritance: Study Notes

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