Question 1

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

Accepted Answer

They produce many offspring and have a short generation time.

Question 2

A cross between a homozygous red-eyed female fruit fly (X$$ ^{W} X$ ^{W} ) $$and a white-eyed male (X$$ ^{w} Y) $$produces F$$_1$$ offspring. What is the expected eye color phenotype of all F$$_1$$ offspring?

Accepted Answer

All offspring will have red eyes.

Question 3

In Morgan’s experiments, the F$$_2$$ generation from a cross between red-eyed females and white-eyed males showed a 3:1 ratio of red to white eyes, but only males had white eyes. What does this observation support?

Accepted Answer

The gene for eye color is X-linked.

Question 4

Which of the following is true about X-linked recessive traits in humans?

Accepted Answer

Males express the trait if they inherit one recessive allele.

Question 5

A woman who is heterozygous for an X-linked recessive disorder (X$$ ^{N} X$ ^{n} ) $$has children with a man who does not have the disorder (X$$ ^{N} Y). $$What is the probability that their son will have the disorder?

Accepted Answer

$$0.25$$

Question 6

Which of the following best describes X chromosome inactivation in female mammals?

Accepted Answer

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

Question 7

A geneticist observes a human karyotype with 47 chromosomes, including three copies of chromosome 21. What is the best description of this condition?

Accepted Answer

Trisomy

Question 8

Which chromosomal abnormality is associated with Turner syndrome?

Accepted Answer

Monosomy X (XO)

Question 9

If nondisjunction occurs during meiosis II in oogenesis, what is the possible chromosomal composition of the resulting gametes?

Accepted Answer

One gamete will have an extra chromosome, one will be missing one, and two will be normal.

Question 10

Which of the following chromosomal alterations results in a segment of a chromosome being reversed end to end?

Accepted Answer

Inversion

Question 11

A male patient is found to have a karyotype of 47 chromosomes, including two X chromosomes and one Y chromosome (XXY). Which syndrome does this represent?

Accepted Answer

Klinefelter syndrome

Question 12

Which of the following best describes polyploidy?

Accepted Answer

A condition where an organism has more than two complete sets of chromosomes.

Question 13

Which of the following is a real-world example of aneuploidy in humans?

Accepted Answer

Down syndrome

Question 14

Which of the following statements about Mendelian traits is correct?

Accepted Answer

They are carried on autosomes and have only two possible alleles per gene.

Question 15

A chromosomal translocation is best described as:

Accepted Answer

A segment of one chromosome moves to a nonhomologous chromosome.

Question 16

In a species with the ZW sex-determination system (such as birds), which sex is heterogametic?

Accepted Answer

Females

Question 17

Which of the following is true regarding Y-linked genes in humans?

Accepted Answer

They are passed from father to all sons.

Question 18

A female cat is heterozygous for fur color, with one allele for black fur and one for orange fur. Due to X-inactivation, her fur shows patches of both colors. What is this phenomenon called?

Accepted Answer

Mosaicism

Question 19

If a deletion occurs in a chromosome, what is the most likely result?

Accepted Answer

A segment of the chromosome is missing.

Question 20

Which of the following best summarizes the chromosomal theory of inheritance?

Accepted Answer

Genes are located on chromosomes, and chromosomes undergo segregation and independent assortment during meiosis.

Chapter 15: The Chromosomal Basis of Inheritance – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards