Sex Determination and Genetics

What is sex determination?

The mechanism by which biological sex is determined.

What are the sex chromosomes in human females?

XX.

What are the sex chromosomes in human males?

XY.

What is the XX-XO system?

XX = female; XO = male.

What is the XX-XY system?

XX = female; XY = male.

What is the ZZ-ZW system?

ZZ = male; ZW = female.

What is the homogametic sex?

The sex possessing two identical sex chromosomes, such as XX females in humans.

What is the heterogametic sex?

The sex possessing different sex chromosomes, such as XY males in humans.

What are pseudoautosomal regions?

Small regions at the tips of the X and Y chromosomes containing genes with alleles on both chromosomes.

What is environmental sex determination?

When environmental factors, such as incubation temperature, influence sex.

What is SRY?

The male-determining gene in humans, normally found on the Y chromosome.

What are sex-linked characteristics?

Traits determined by genes located on sex chromosomes.

What is an X-linked characteristic?

A trait controlled by a gene located on the X chromosome.

What is a Y-linked characteristic?

A trait controlled by a gene located on the Y chromosome.

Why are X-linked traits often expressed differently in males?

Males have only one X chromosome, so they have only one copy of an X-linked gene.

What does hemizygous mean?

Having only one copy of a particular gene, as males do for many X-linked genes.

What is a reciprocal cross?

A cross in which the sexes of the parents are reversed while keeping the same genotypes.

What type of inheritance is red-green color blindness?

X-linked recessive.

What genotype is a color-blind male?

XᶜY.

What genotypes can a normal-vision female have?

X⁺X⁺ or X⁺Xᶜ.

What genotype is a color-blind female?

XᶜXᶜ.

What genotype is a normal-vision male?

X⁺Y.