Figure 5.3 Autosomal inheritance of CYP2D6 polymorphism (debrisoquine/spar-sparteine hydroxylation polymorphism).

Most X-linked traits are recessive, or partly recessive. Affected persons are mostly males born of carrier females. They are related to each other through female carrier relatives with a maternal grandfather and grandson being affected, or a maternal uncle and nephew being affected. Among genetic disorders that cause disease, if a recessive trait is harmful, it is usually rare; if it is not very harmful, it may be fairly common. The example chosen to represent a sex-linked pharmacogenetic trait, G6PD deficiency (Figure 5.4),29 is very common in certain ethnic populations; the severity of the phenotype depends on the nature of the

Table 5.5 Expected Segregation Frequencies among Children with Autosomal and Sex-(X)-Linked Traits

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