Inheritance in Single-Gene Disorders

Autosomal recessive inheritance is often observed with enzyme deficiencies, where heterozygotes express 50% of normal activity. 

Both parents of an affected person for an autosomal recessive disorder must have one normal and one mutant allele, making them obligate carriers barring very rare new mutations. 

The likelihood of a person being homozygous for an autosomal recessive trait increases in consanguineous matings because of the existence of a common ancestor. 

Rare autosomal recessive diseases also occur with high frequency among genetically isolated populations due to inbreeding. 

TAYS-SACHS DI6EASE IN A GENETICALLY ISOLATED POPULATION 

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