Final answer:
X-linked recessive traits are more frequently observed in males due to hemizygosity. Males have only one X chromosome, so any recessive allele on that chromosome will result in the expression of the trait, while females must inherit recessive alleles from both parents to express the trait.
Step-by-step explanation:
Understanding X-Linked Recessive Traits in Humans and Drosophila In humans and Drosophila, X-linked recessive traits are observed more frequently in males than in females. This is because males are hemizygous with respect to the X chromosome, meaning they have only one X chromosome and therefore one allele for X-linked traits. As a result, the presence of a recessive allele on a male's X chromosome will invariably express that trait, as there is no corresponding allele on the Y chromosome to potentially mask its expression. In contrast, females have two X chromosomes and are homozygous or heterozygous for X-linked traits.
To express a recessive trait, a female must inherit two recessive alleles, one from each parent. However, if a female is heterozygous—carrying one recessive and one dominant allele—she often does not express the trait but can still pass the recessive allele to her offspring.Conditions such as color blindness, hemophilia, and muscular dystrophy are examples of disorders linked to the X chromosome. Females can be carriers of these disorders and may pass the genes onto their offspring, with male children being more likely to express the disorders, thus showing the traits more in males due to their hemizygosity.