Lecture 21: Human Genetic Disease

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since 29 September 1999

(version 23 September, 1999)

Symbols Used in Pedigree Analysis:

1. Inheritance of an autosomal recessive mutation

Examples: cystic fibrosis (CF), phenylketonuria (PKU).

(2) Inheritance of an autosomal dominant mutation:

Examples: Huntington’s disease, Lou Gehrig disease (amyotropic lateral sclerosis or ALS)

(3) Inheritance of an X-linked recessive mutation:

Examples: hemophilia, red-green color blindness.

4. Inheritance of an X-linked dominant mutation

Examples: hypophosphatemia, few other examples.

Dominance and recessiveness

Pedigrees do not tell us anything about the molecular nature of the defect. e.g., Dominant mutations often are gain-of-function mutations; recessive mutations often are loss-of-function mutations. But retinoblastoma (lecture 19) and osteogenesis imperfecta are both inherited as dominant mutations, although they are caused by loss-of-function mutations.