3. Extensions to Mendelian Inheritance

How do we know that in humans the X chromosomes play no role in human sex determination, while the Y chromosome causes maleness and its absence causes femaleness?

How do we know whether or not a heteromorphic chromosome such as the Y chromosome plays a crucial role in the determination of sex?

Write a short essay that discusses sex chromosomes as they contrast with autosomes.

Distinguish between the concepts of sexual differentiation and sex determination.

Contrast the XX/XY and XX/X0 modes of sex determination.

Describe the major difference between sex determination in Drosophila and in humans.

How do mammals, including humans, solve the 'dosage problem' caused by the presence of an X and Y chromosome in one sex and two X chromosomes in the other sex?

What specific observations (evidence) support the conclusions about sex determination in Drosophila and humans?

How many Barr bodies are found in a normal human female nucleus? In a normal male nucleus?

An insect species is discovered in which the heterogametic sex is unknown. An X-linked recessive mutation for reduced wing (rw) is discovered. Contrast the F₁ and F₂ generations from a cross between a female with reduced wings and a male with normal-sized wings when the female is the heterogametic sex.

An insect species is discovered in which the heterogametic sex is unknown. An X-linked recessive mutation for reduced wing (rw) is discovered. Contrast the F₁ and F₂ generations from a cross between a female with reduced wings and a male with normal-sized wings when the male is the heterogametic sex.

Consider the case where a mutation occurs that disrupts translation in a single human mitochondrion found in the oocyte participating in fertilization. What is the likely impact of this mutation on the offspring arising from this oocyte?

What is the basis for homology among chromosomes?

It has been suggested that any male-determining genes contained on the Y chromosome in humans cannot be located in the limited region that synapses with the X chromosome during meiosis. What might be the outcome if such genes were located in this region?