Exam 5: Sex Determination and Sex Chromosomes

In humans, the genetic basis for determining the sex "male" is accomplished by the presence of ________.

Glucose -6 -phosphate dehydrogenase (G6PD) deficiency is inherited as an X -linked recessive gene in humans. A woman whose father suffered from G6PD marries a normal man. a() What proportion of their sons is expected to be G6PD? b() If the husband were not normal but were G6PD deficient, would you change your answer in part (a)?

Dosage compensation is accomplished in humans by inactivation of the Y chromosome.

The sex of birds, some insects, and other organisms is determined by a ZW chromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XY in humans). Assume that a recessive lethal allele on the Z chromosome causes death of an embryo in birds. What sex ratio would result in the offspring if a cross were made between a male heterozygous for the lethal allele and a normal female?

One form of hemophilia is caused by a sex -linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that their first son will have hemophilia?

In Drosophila, the female is the heterogametic sex.

A recessive gene for red -green color blindness is located on the X chromosome in humans. Assume that a woman with normal vision (her father is color -blind) marries a color -blind male. What is the likelihood that this couple's first son will be color -blind?

Assume that you are told that a particular organism, Drosophila, has the XO chromosome complement. You are also told that the autosomal complement is a normal 2n. You know that in humans the XO complement is female determining. Would you be correct in assuming that the Drosophila sex for XO is also female? Choose the answer that includes the correct explanation.

One form of hemophilia is caused by a sex -linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia? (Note: In this problem, you must Include the probability of having a daughter in your computation of the final probability.)

An individual with Klinefelter syndrome generally has one Barr body.

What can cause phenotypic mosaicism for X -linked genes in female mammals?

A small part of the human Y chromosome contains the gene that is responsible for determining maleness. What is the name of this gene?

In Drosophila, an individual female fly was observed to be of the XXY chromosome complement (normal autosomal complement) and to have white eyes as contrasted with the normal red eye color of wild type. The female's mother and father had red eyes. The mother, however, was heterozygous for the gene for white eyes. Knowing that white eyes are X -linked and recessive, present an explanation for the genetic and chromosomal constitution of the XXY, white -eyed individual. It is important that you state in which parent and at what stage the chromosomal event occurred that caused the genetic and cytogenetic abnormality.

Sex -limited genes cause males to be males and females to be females.

What is the composition of a Barr body?

The Protenor mode of sex determination is the _.

What particular karyotype was once considered to be related to criminal predisposition?

How many Barr bodies would one expect to see in cells of Turner syndrome females and Klinefelter syndrome males?

An individual with Turner syndrome has no Barr bodies.

In Drosophila, the sex of a fly with the karyotype XO:2A is _.