Question

how are the alleles for sex - linked traits inherited?
they are passed from the y chromosome in parents to the x chromosome in offspring.
they are passed from the x chromosome in parents to the xy chromosome in offspring.
they are passed from parents to offspring on the x and y chromosomes.
they are passed from any chromosome in the parents to the x or y chromosome in the offspring.

Explanation:

Sex - linked traits are associated with genes on the sex chromosomes (X and Y). Alleles for these traits are passed from parents to offspring on the X and Y chromosomes. For example, in humans, males have XY chromosomes and females have XX. Traits like color - blindness (a sex - linked recessive trait) are carried on the X chromosome. Males (XY) can inherit the allele on their single X chromosome (from the mother, as the father gives the Y). Females (XX) inherit one X from each parent. The Y chromosome also has some sex - linked genes (e.g., for male - specific development). So, alleles for sex - linked traits are passed on the X and Y chromosomes from parents to offspring.

Answer:

They are passed from parents to offspring on the X and Y chromosomes.