BIO207H5 Lecture Notes - Lecture 8: Murray Barr, Wild Type, Chromosome
Document Summary
In x-linked recessive inheritance, females homozygoous for the recessive allele or males hemizygous for it display the recessive phenotype. In x-linked dominant traits, heterozygous females and males hemizygous for the dominant allele express the dominant phenotype: hemizygous males display any allele on their single x whether the allele is recessive or dominant in females. Expression of x-linked recessive traits: a hallmark of recessive x-linked inheritance is the expression of the trait much more often in males than in females. There are numerous x-linked recessive traits in humans. Hemophilia a is an x-linked recessive trait: hemophilia a is caused by a mutation in the factor viii gene on the x chromosome. The mutant allele produces a nonfunctional blood-clotting protein: a de novo (newly occurring) mutation is thought to have been passed from queen victoria of england to some of her offspring. Congenital hypertrichosis: congenital hypertrichosis (cgh) is a rare x-linked dominant disorder in humans.
