Hypertrichosis

X-Linked Dominant

Background:

Your students should already be familiar with the much more common mode of X-linked recessive inheritance. In hypertrichosis, however, an X-linked dominant disorder affected males and females both exhibit the condition, although heterozygous females may be less severe. In fact, women may exhibit lyonization (as is described under anhidrotic ectodermal dysplasia) giving a rather patchy expression of the trait.

Perhaps this rare trait is an atavism-- the reappearance of an ancestral characteristic lost through time and evolution. This possibility may be mentioned during an evolution unit as well.

Activity:

After introduction to X-linked recessive traits, Students should be divided into groups to make up a pedigree that would show how a trait would be passed along if it were inherited in an X-linked dominant manner. Once they have designed a pedigree tell them about this disorder.

For more information visit Online Mendelian Inheritance in Man

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