Exam 7: Sex Determination and Sex Chromosomes

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.)

Describe an experiment in which transgenic mice were used to identify the male-determining region of the Y chromosome.

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?

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?

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

Klinefelter and Turner syndromes have how many chromosomes,respectively?

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)?

Assuming a normal number of autosomes,what would be the sex of the following: XXY mouse,XXY Drosophila?

Klinefelter syndrome in humans,which leads to underdeveloped testes and sterility,is caused by which chromosomal condition?

In Drosophila,sex is determined by the ratio of the number of X chromosomes to the number of haploid sets of autosomes.

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?

The Lygaeus mode of sex determination is the ________.

In Drosophila,the female is the heterogametic sex.

A color-blind,chromatin-positive male child (one Barr body)has a maternal grandfather who was color blind.The boy's mother and father are phenotypically normal.Construct and support (using appropriately labeled diagrams)a rationale whereby the chromosomal and genetic attributes of the chromatin-positive male are fully explained.

In humans,the male is the homogametic sex.

A color-blind woman with Turner syndrome (XO)has a father who is color blind. Given that the gene for the color-blind condition is recessive and X-linked,provide a likely explanation for the origin of the color-blind and cytogenetic conditions in the woman.

Dosage compensation leads to a variety of interesting coat color patterns in certain mammals.For instance,a female cat that is heterozygous for two coat color alleles,say black and orange,will usually have the "calico" or mosaic phenotype.Describe the chromosomal basis for the mosaicism (calico)in the female.Explain why chromosomally normal male cats do not show the mosaic phenotype,but XXY male cats can be calico.

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?

A typical XX human female has one Barr body.