Sex-Linked Traits Overview

Sex-Linked Traits Overview

• Males are more likely to express recessive, sex-linked traits due to their single X chromosome.
• Sons inherit recessive, sex-linked traits specifically from their mothers, who may be carriers.

X Chromosome and Sex-Linked Traits

• Most sex-linked traits are located on the X chromosome.
• Colorblindness in humans is a common example, caused by a recessive allele (Xn for colorblindness, XN for normal vision).

Colorblindness Example

• A colorblind man (genotype XnY) with a carrier woman (genotype XNXn) has potential offspring combinations.
• Each child has a 50% chance of being colorblind.
• There is a 50% chance of a daughter being a carrier and a 50% chance of a son being colorblind.

Eye Color in Fruit Flies

• Red eyes (XR) are dominant over white eyes (Xr) in fruit flies.
• A red-eyed male (genotype XRY) mating with a white-eyed female (genotype XrXr) can produce offspring.
• Offspring's probability of having white eyes is 50%.

Hemophilia and X-Linked Inheritance

• Hemophilia is caused by a recessive gene on the X chromosome (Xn = affected, XN = not affected).
• A man with hemophilia (genotype XnY) marries a homozygous dominant woman (genotype XNXN).
• None of the offspring will inherit hemophilia as the mother does not carry the recessive allele.

Feather Color in Chickens

• In chickens, barred feathers (ZB) dominate over non-barred feathers (Zb).
• A barred male (genotype ZBW) with a non-barred female (genotype ZbZb) has specific offspring probabilities.
• There is a 0% chance for non-barred males and a 100% chance for barred females.

Summary of Probabilities

• For barred chickens: 100% females will be barred if they inherit ZB from the male.
• Non-barred females and males will have a respective probability of 0% and 100% depending on parental genotypes.