X-linked recessive disorders are more common in males – why?

X-linked recessive disorders are more common in males – why? A Male has one X chromosome and one Y chromosome. The single recessive gene resides on the X chromosome. The Y chromosome doesn’t contain most of the genes on the X chromosome. Because of that, it can’t protect the male from a genetic disorder. Diseases such as haemophilia, and colour blindness occur from a recessive gene on the X chromosome.

X-linked recessive disorders are more common in males – reasons

X and Y chromosomes determine the sex of a human being. Males have one X chromosome and one Y chromosome. And, females have two X chromosomes. The gene of X-linked recessive disorder is passed down on the X chromosome. Since it is passed down on the X chromosome, this type of disorder is more common in men.

X-linked recessive disorders are more common in males. The reason behind this is described below.

The single recessive gene (allele) resides on the X chromosome in case of X-linked recessive disorders. Males have one X chromosome and one Y chromosome. (The Males have only one X chromosome, from their mother.) Now say, the single X chromosome of a male has the recessive disorder allele like haemophilia. The Y chromosome doesn’t contain most of the genes on the X chromosome. Because of that, there is no corresponding allele on their Y chromosome to mask the recessive disorder allele on the X chromosome of a male. Hence the males will have this X-linked recessive disorder.

Females have two X chromosomes, one from their mother and one from their father. As the disorder gene (allele) is recessive, to have the disorder in females both X chromosomes would need to have the gene (allele) responsible for the X-linked recessive disorder, like haemophilia. Hence, this type of disorder is more common in men.

Haemophilia is X linked recessive disorder. The responsible gene is passed down on the X chromosome and the disorder is more common in men. Males have no corresponding allele on their Y chromosome to mask the allele carried on their X chromosome.

Related study: Alleles and Genotypes for human blood groups – multiple allelism in ABO

X-linked recessive disorders are more common in males – why?
Scroll to top
error: physicsTeacher.in