Question 1

Which of the following best describes the mechanism of dosage compensation in female mammals?

Accepted Answer

Random inactivation of one X chromosome in each somatic cell

Question 2

A male patient is diagnosed with hemophilia, an X-linked recessive disorder. If his partner is a carrier, what is the probability that their son will also have hemophilia? Use the following genotypes: Xᴴ = normal, Xʰ = hemophilia.

Accepted Answer

$$\frac{1}{2}$$

Question 3

Which gene is responsible for initiating testis development in humans, and on which chromosome is it located?

Accepted Answer

SRY gene on the Y chromosome

Question 4

In the ZW sex determination system, which of the following is true?

Accepted Answer

Females are heterogametic (ZW)

Question 5

A calico (tortoiseshell) cat displays both black and orange fur patches. Which genetic phenomenon explains this pattern?

Accepted Answer

X-inactivation (Lyonization)

Question 6

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

Accepted Answer

Males only need one copy of the mutant allele to express the trait

Question 7

In the XO sex determination system, which of the following is true for males?

Accepted Answer

They have only one X chromosome and no Y chromosome

Question 8

A woman who is heterozygous for the X-linked gene for color blindness (XᴮXᵇ) marries a man with normal vision (XᴮY). What is the probability that their daughter will be color blind?

Accepted Answer

$$0$$

Question 9

Which historical scientist is credited with the discovery of sex-linked inheritance through experiments with Drosophila melanogaster?

Accepted Answer

Thomas Hunt Morgan

Question 10

In haplodiploidy sex determination, which of the following is true?

Accepted Answer

Males are haploid and develop from unfertilized eggs

Question 11

A female with genotype XᴴXʰ (carrier for hemophilia) and a male with genotype XʰY (hemophiliac) have children. What is the probability that a son will have hemophilia?

Accepted Answer

$$\frac{1}{2}$$

Question 12

Which of the following best explains why X-inactivation leads to mosaic phenotypes in female mammals?

Accepted Answer

X-inactivation occurs randomly in each cell during early development

Question 13

Which of the following is a direct consequence of the SRY gene's action during human embryonic development?

Accepted Answer

Development of Wolffian ducts into male reproductive organs

Question 14

A woman with normal vision (XᴮXᴮ) and a man with color blindness (XᵇY) have children. What is the expected phenotype of their sons?

Accepted Answer

All sons will have normal vision

Question 15

Which of the following disorders is caused by a deficiency in blood clotting factors and is inherited as an X-linked recessive trait?

Accepted Answer

Hemophilia

Question 16

If a gene is located on the X chromosome and is recessive, what is the genotype of a female who is a carrier but does not express the trait?

Accepted Answer

XᴬXᵃ

Question 17

Which of the following best describes the inheritance pattern observed in Morgan's Drosophila white-eye experiment?

Accepted Answer

Sex-linked recessive

Question 18

Which of the following is NOT a mechanism of chromosomal sex determination?

Accepted Answer

ABO system

Question 19

Which of the following statements about Barr bodies is correct?

Accepted Answer

They are inactivated X chromosomes

Question 20

A female cat is heterozygous for the X-linked orange and black fur alleles. What is the expected phenotype?

Accepted Answer

Tortoiseshell (patches of black and orange)

Sex Linkage & Determination: Genetics Study Notes

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