Question 1

During the evolution of the human Y chromosome, all of the following are assumed to occur EXCEPT:

Accepted Answer

During the evolution of the Y chromosome, genes responsible for critical cellular functions did not move to the Y chromosome; instead, they remained on the X chromosome or were lost.

Question 2

Suppose that an apparently female athlete fails a gender test and is not allowed to compete in her event. The gender test is based on examination of cheek cells for the presence of one or more Barr bodies. Later, it is discovered that the athlete has androgen-insensitivity syndrome. What is the chromosome constitution of a person with androgen-insensitivity syndrome?

Accepted Answer

The answer of Suppose that an apparently female athlete fails...

Question 3

Red-green color blindness is X-linked recessive. A woman with normal color vision has a father who is color blind. The woman has a child with a man with normal color vision. Which phenotype is NOT expected?

Accepted Answer

A color-blind female is not expected because the mother is a carrier (X^NX^c) and the father has normal vision (X^NY). A color-blind female would require two X^c alleles, which is not possible with this parental combination.

Question 4

Familial vitamin-D-resistant rickets is an X-linked dominant condition in humans. If a man is afflicted with this condition and his wife is normal, it is expected that among their children, all the daughters would be affected and all the sons would be normal. In families where the husband is affected and the wife is normal, this is almost always the outcome among their children when such families have been studied. Very rarely an unexpected result occurs in such families where a boy is born with the disorder. If the chromosomes of such unusual boys are examined, what might be expected to be found?

Accepted Answer

The presence of an extra X chromosome (XXY) could result in a boy inheriting the X-linked dominant condition from his father, as he would have two X chromosomes, one of which could carry the mutation.

Question 5

A man and a woman are trying to have children but are unsuccessful. The man's autosomes appear normal, but his sex chromosomes, shown in the following diagram, are not. The diagram also shows a normal male's sex chromosomes for reference. In two to three sentences, explain the man's situation, including the type of chromosome mutation he carries, the specific regions of specific chromosomes involved, and why he is male.

Accepted Answer

The answer of A man and a woman are trying...

Question 6

Some organisms have multiple X and Y chromosomes and even different numbers of X and Y chromosomes. You have discovered such a species. Females have 8 X chromosomes, whereas males have 4 X and 2 Y. Describe the X and Y constitution of the gametes produced by this species-both male and female-that allows these chromosome numbers to be stably maintained.

Accepted Answer

The answer of Some organisms have multiple X and Y...

Question 7

While doing summer fieldwork on a remote Indonesian island, you discover a new genus of lizard closely related to Komodo dragons. You attempt to discover what sex determination system it uses by performing a series of controlled crosses on the island, using an isolated pair of lizards. Initially, all your crosses yield only males (in significant numbers). As fall begins and you prepare to leave the island, you find that your last cross yielded only females (in significant numbers). Suggest a mode of sex determination that explains these data.

Accepted Answer

The answer of While doing summer fieldwork on a remote...

Question 8

Explain the development of female external anatomy in individuals with androgen-insensitivity syndrome.

Accepted Answer

The answer of Explain the development of female external anatomy...

Question 9

Suppose that an apparently female athlete fails a gender test and is not allowed to compete in her event. The gender test is based on examination of cheek cells for the presence of one or more Barr bodies. Later, it is discovered that the athlete has androgen-insensitivity syndrome. Evaluate the decision of the officials to exclude the athlete from athletic competition as a female in light of your knowledge of androgen-insensitivity syndrome. Do you think the athlete should be allowed to compete as a female?

Accepted Answer

The answer of Suppose that an apparently female athlete fails...

Question 10

Explain the genders of human and diploid DrosophilaXXY individuals.

Accepted Answer

The answer of Explain the genders of human and diploid...

Question 11

A man and a woman are trying to have children but are unsuccessful. The man's autosomes appear normal, but his sex chromosomes, shown in the following diagram, are not. The diagram also shows a normal male's sex chromosomes for reference. Can you tell if the mutation came from the man's mother or the man's father? Explain how you can tell.

Accepted Answer

The answer of A man and a woman are trying...

Question 12

What level of male hormones would you expect to find in a person with androgen-insensitivity syndrome?

Accepted Answer

The answer of What level of male hormones would you...

Question 13

List five different sex determination systems and a representative organism for each.

Accepted Answer

The answer of List five different sex determination systems and...

Question 14

Suppose that an apparently female athlete fails a gender test and is not allowed to compete in her event. The gender test is based on examination of cheek cells for the presence of one or more Barr bodies. Later, it is discovered that the athlete has androgen-insensitivity syndrome. Explain why the athlete failed the gender test. What did the technician see in the test and how was it interpreted?

Accepted Answer

The answer of Suppose that an apparently female athlete fails...

Question 15

Predict the sexual phenotype of a person who is XY but whose Y chromosome carries a deletion of the SRY gene. Explain your prediction.

Accepted Answer

The answer of Predict the sexual phenotype of a person...

Question 16

Explain the genders of human and diploid Drosophila XO individuals.

Accepted Answer

The answer of Explain the genders of human and diploid...

Question 17

Characterize the gonads of a person with androgen-insensitivity syndrome as testes, ovaries, or intersex.

Accepted Answer

The answer of Characterize the gonads of a person with...

Question 18

How might an XY person with a deletion of the SRY gene be distinguished from a person with androgen-insensitivity syndrome?

Accepted Answer

The answer of How might an XY person with a...

Question 19

In Drosophila, flies that are XXY but have a normal diploid set of autosomes have been found. Such XXY chromosome constitutions have also been found in humans. The sex of such individuals is expected to be:

Accepted Answer

The answer of In Drosophila, flies that are XXY but...

Question 20

Which statement BEST summarizes our current understanding of the origin of the Y chromosome?

Accepted Answer

The Y chromosome is believed to have originated from a pair of autosomes, evolving alongside the X chromosome, with one of the pair undergoing significant changes to become the Y chromosome.

Quiz 4: Sex Determination and Sex-Linked Characteristics

During the evolution of the human Y chromosome, all of the following are assumed to occur EXCEPT:

Red-green color blindness is X-linked recessive. A woman with normal color vision has a father who is color blind. The woman has a child with a man with normal color vision. Which phenotype is NOT expected?

Explain the development of female external anatomy in individuals with androgen-insensitivity syndrome.

Explain the genders of human and diploid DrosophilaXXY individuals.

What level of male hormones would you expect to find in a person with androgen-insensitivity syndrome?

List five different sex determination systems and a representative organism for each.

Predict the sexual phenotype of a person who is XY but whose Y chromosome carries a deletion of the SRY gene. Explain your prediction.

Explain the genders of human and diploid Drosophila XO individuals.

Characterize the gonads of a person with androgen-insensitivity syndrome as testes, ovaries, or intersex.

How might an XY person with a deletion of the SRY gene be distinguished from a person with androgen-insensitivity syndrome?

In Drosophila, flies that are XXY but have a normal diploid set of autosomes have been found. Such XXY chromosome constitutions have also been found in humans. The sex of such individuals is expected to be:

Which statement BEST summarizes our current understanding of the origin of the Y chromosome?