Answer:
a) these traits are carried only on the x chromosome and since there is no matching gene on the y chromosome, the traits are expressed more readily in males.
Explanation:
Hemophilia, color blindness, and duchenne muscular dystrophy are disorders which are caused by X-linked recessive mutations which means that even if a mutation occurs in a gene of only one X chromosome then the phenotype will be expressed in the males because they are hemizygous for the gene. By hemizygous we mean to say that males have one X and one Y chromosome so a gene present on X chromosome will not find match on the Y chromosome and the mutation will express readily.
In contrast to this, in case of females who have two X chromosomes, the mutation in one X chromosome may be suppressed by another X chromosome in heterozygous condition i.e. if another X chromosome has healthy gene (wild type gene). In case of females the diseased phenotype will only appear if they are homozygous for the mutation.
