"Inborn Errors of Metabolism" in Humans
one of these metabolic disorders are due to insufficiency
of the enzyme activity involved, in individuals homozygous
for the allele: they are therefore recessive conditions. The
exception is that alteration of PRPP synthetase increases
enzyme activity: this still occurs only in homozygotes for
the modified allele, so the condition is still described as recessive.
Figure © 2000
al. ; All text
material © 2012 by Steven M.