Final answer:
A sex-linked trait is more commonly observed in males because they only need one recessive allele from their mother to express the trait. Females must inherit recessive alleles from both parents to express the trait and are often carriers if they inherit one recessive allele.
Step-by-step explanation:
When a trait is sex-linked, it will show up in greater numbers in males and it will have been inherited from the mother. Sex-linked traits are usually linked to genes located on the X chromosome. Since males (XY) have only one X chromosome, they are hemizygous for the X-linked genes and will express the trait if they inherit a recessive allele. In contrast, females (XX) must inherit two copies of the recessive allele, one from each parent, to express the trait. Carrier females, who have one recessive X-linked allele, can pass the trait to their sons, making it more common in males.
X-linked recessive disorders such as red-green color blindness, and Types A and B hemophilia are more commonly observed in males because they only need to inherit one mutant allele to be affected. Carrier females tend to be unaffected but can contribute the recessive allele to their offspring, thus passing the trait to their sons, who will exhibit the trait, or passing the carrier status to their daughters.