Question

Why do sex-linked traits follow different patterns of inheritance than other traits? A. Males have two X chromosomes, and females only have one. B. Males cannot carry recessive alleles for sex-linked traits. C. Males carry two copies of every sex-linked gene. D. Males only need one recessive allele to have a recessive sex-linked trait.

Answer 1

D.  Males only need one recessive allele to have a recessive sex-linked trait.

Since males have one X chromosome and one Y chromosome, a recessive allele on either chromosome lead to pheontypic expression of that gene.

Answer 2

Answer:

The correct answer would be D. Males only need one recessive allele to have a recessive sex-linked trait.

Traits which are inherited as autosomal recessive trait need the presence of two copies of the recessive allele in order to produce the phenotype.

In contrast, in sex-linked traits, only a single copy of recessive allele is enough to produce the phenotype in males. It is because the males are heterozygous in terms of sex chromosome.  

They carry one copy of the X chromosome and one copy of the Y chromosome. So, only a single copy of allele is enough to produce the phenotype.

For example, hemophilia is X-linked recessive disorder which requires only one copy of recessive allele to produce the phenotype in males, that is, $X^{h}Y$.