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

Thomas Hunt Morgan’s experiments with Drosophila melanogaster provided the first solid evidence for what genetic principle?

Accepted Answer

Genes are located on chromosomes.

Question 3

In Morgan’s fruit fly experiments, the wild-type eye color was red. If a white-eyed male is crossed with a red-eyed female, and all F1 offspring have red eyes, what does this suggest about the inheritance of eye color?

Accepted Answer

Red eye color is dominant and likely X-linked.

Question 4

Which of the following best explains why males are more likely to express X-linked recessive disorders such as color blindness?

Accepted Answer

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

Question 5

A woman who is a carrier for red-green color blindness (X	extsuperscript{N}X	extsuperscript{n}) has children with a man who is colorblind (X	extsuperscript{n}Y). What percentage of their sons are expected to be colorblind?

Accepted Answer

$$50\%$$

Question 6

Which of the following is a direct result of X-inactivation in female mammals?

Accepted Answer

One X chromosome in each cell is randomly inactivated, forming a Barr body.

Question 7

A calico cat displays patches of orange and black fur. Which genetic mechanism explains this pattern?

Accepted Answer

Random X chromosome inactivation in heterozygous females.

Question 8

Linked genes tend to be inherited together because:

Accepted Answer

They are located near each other on the same chromosome.

Question 9

If two genes are very close together on the same chromosome, what is the expected effect on the frequency of recombination between them?

Accepted Answer

The frequency of recombination will be low.

Question 10

Which chromosomal abnormality is responsible for Down syndrome?

Accepted Answer

Trisomy of chromosome 21

Question 11

A diploid cell undergoes nondisjunction during meiosis II. What is the most likely outcome for the resulting gametes?

Accepted Answer

Half the gametes will have an abnormal chromosome number.

Question 12

Which of the following chromosomal alterations is most likely to be lethal if homozygous in a diploid organism?

Accepted Answer

Deletion

Question 13

A geneticist observes a plant species with four complete sets of chromosomes (4n). This condition is best described as:

Accepted Answer

Tetraploidy

Question 14

Which of the following best describes the difference between autosomes and sex chromosomes in humans?

Accepted Answer

Autosomes are the same in both sexes, while sex chromosomes differ between males and females.

Question 15

A male with Klinefelter syndrome has which of the following sex chromosome compositions?

Accepted Answer

XXY

Question 16

Which of the following is NOT a possible result of a chromosomal translocation?

Accepted Answer

A segment of a chromosome is reversed within the same chromosome.

Question 17

In a cross between a woman who is not a carrier for hemophilia (X	extsuperscript{H}X	extsuperscript{H}) and a man with hemophilia (X	extsuperscript{h}Y), what is the probability that their daughters will have hemophilia?

Accepted Answer

$$0\%$$

Question 18

Which of the following best explains why plants can often tolerate polyploidy, while animals usually cannot?

Accepted Answer

Plants can survive with extra sets of chromosomes, which may even lead to new species.

Question 19

Which of the following is a real-world example of a sex-linked disorder caused by a mutation in a blood clotting factor gene?

Accepted Answer

Hemophilia A

Question 20

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, leading to different alleles being expressed in different cells.

The Chromosomal Basis of Inheritance: Study Guide

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