Final answer:
Recessive X-linked diseases are more common in males due to their single X chromosome, which expresses any recessive allele present, while females need two copies of the recessive allele to express the disease and often are just carriers.
Step-by-step explanation:
Many recessive X-linked diseases occur more frequently in males because males only have one X chromosome, and a recessive allele on the X chromosome will be expressed, since there is no corresponding allele on a Y chromosome to potentially mask it. Females, on the other hand, have two X chromosomes, so they must inherit two copies of the recessive allele, one from each parent, to express the trait. Often, females are carriers with one normal and one mutant allele, not expressing the disease themselves but able to pass the mutant allele to their offspring. Disorders such as color blindness, hemophilia, and certain forms of muscular dystrophy are examples of X-linked recessive diseases.