Inborn Errors of Metabolism
The so-called Inborn Errors of
Metabolism are those genetic disorders first identified
as deficiencies of particular enzymes. These were listed in
Victor McKusick's (1921 - 2008) "Mendelian
Inheritance in Man" (1st ed, 1966), organized by
Entry numbers as dominant, recessive, and X-
or Y-linked. Other phenotypes thought to be
connected with genotype, such as handedness, eye color, and
hairy
ears were included.
The first slim edition grew to two thick volumes in the 12th edition of 1998, before going entirely online (OMIM). Single-locus enzymatic phenotypes are assigned to a particular physical position (Locus) on the map of each chromosome. For example, the locus for Phenylalanine Hydroxylase (PAH) involved with Phenylketonuria (PKU) occurs on the long arm (q) of Chromosome 12 (12q) in band 24.1 of the Denver system (12q24.1). With the completion of the Human Genome Project in 2003, precise bounds of the locus and nucleotide variants (SNPs) are included.