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Frequency of Autosomal Recessive Disease in Consanguineous Mating

Description

The frequency of an autosomal recessive disease in the offspring of a consanguineous mating can be calculated based on the frequency of the disease in the general population and the inbreeding coefficient for the mating.


 

For an autosomal recessive disease:

 

frequency of a defective gene =

= SQRT(frequency of disease in general population)

 

frequency of disease in a consanguineous mating =

= (frequency of disease in general population) + ((1 - (frequency of defective gene)) * (frequency of defective gene) * F)

 

where:

• F = inbreeding coefficient for consanguineous mating

• frequency of nondefective gene = 1 - (frequency of defective gene)

Consanguineous Mating

Proportion of Shared Alleles

F

parent and offspring

1/2

1/4

brother and sister

1/2

1/4

half siblings

1/4

1/8

uncle and niece

1/4

1/8

aunt and nephew

1/4

1/8

first cousins

1/8

1/16

double first cousins

1/4

1/8

half first cousins

1/16

1/32

first cousins once removed

1/16

1/32

second cousins

1/32

1/64

second cousins once removed

1/64

1/128

third cousins

1/128

1/256

Table 15-5, page 352, Keats 1996

 


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Specialty

ICD-10