Question 1

Which chromosome is responsible for carrying the SRY gene that determines male development in humans?

Accepted Answer

Y chromosome

Question 2

In the X-Y system of sex determination, which statement best explains why X-linked recessive disorders are more common in males?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will be expressed.

Question 3

A female carrier for color blindness (X$$^NX$^n) $$mates with a male with normal vision (X$$^NY). $$What is the probability that their son will be color blind?

Accepted Answer

$$50\%$$

Question 4

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

Accepted Answer

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

Question 5

If a male with color blindness (X$$^nY) $$mates with a female who is homozygous dominant for normal vision (X$$^NX$^N$$), what will be the phenotype of their daughters?

Accepted Answer

All daughters will be carriers but have normal vision.

Question 6

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

Accepted Answer

XIST gene

Question 7

In calico cats, the mosaic pattern of fur color is a result of which genetic phenomenon?

Accepted Answer

Random X-chromosome inactivation

Question 8

Which of the following is NOT a characteristic of Y-linked genes?

Accepted Answer

They are found on the X chromosome.

Question 9

A female who is heterozygous for an X-linked gene will exhibit which of the following in her somatic cells?

Accepted Answer

Some cells express the dominant allele, others express the recessive allele due to X inactivation.

Question 10

Which equation represents the probability that a son will inherit an X-linked recessive disorder from a carrier mother and a normal father?

Accepted Answer

$$P = 0.5$$

Question 11

Which of the following statements about the Barr body is correct?

Accepted Answer

It is an inactive X chromosome found in female cells.

Question 12

Which system of sex determination is found in birds, some fishes, and some insects?

Accepted Answer

Z-W system

Question 13

A female carrier for hemophilia (X$$^HX$^h) $$mates with a male who has hemophilia (X$$^hY). $$What is the probability that their daughter will have hemophilia?

Accepted Answer

$$50\%$$

Question 14

Which of the following best describes the inheritance pattern of Duchenne muscular dystrophy?

Accepted Answer

X-linked recessive

Question 15

If a female bee develops from a fertilized egg, what is her ploidy level?

Accepted Answer

Diploid

Question 16

Which of the following is a real-world consequence of X-chromosome inactivation in humans?

Accepted Answer

Females can be genetic mosaics for X-linked traits.

Question 17

Which formula would you use to calculate the probability that a daughter will be a carrier for an X-linked recessive disorder if her mother is a carrier and her father is normal?

Accepted Answer

$$P = 0.5$$

Question 18

Which of the following statements about sex-linked genes is correct?

Accepted Answer

They can be found on either the X or Y chromosome.

Question 19

Which of the following best explains why calico cats are almost always female?

Accepted Answer

X-chromosome inactivation leads to mosaic expression of fur color genes.

Question 20

Which of the following is a plausible outcome if a female carrier for color blindness mates with a color-blind male?

Accepted Answer

Each child has a 50% chance of being color blind, regardless of sex.

The Chromosomal Basis of Inheritance: Sex-Linked Genes and X Inactivation

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