Methodology in medical genetics : an introduction to statistical methods / Alan E.H. Emery.

  • Emery, Alan E. H.
Date:
1986
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Methodology in medical genetics : an introduction to statistical methods / Alan E.H. Emery. Source: Wellcome Collection.

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    6 METHODOLOGY IN MEDICAL GENETICS But this is only true when p is almost unity, otherwise H = 2pq = 2(1 - q)q = 2q- Iq^ 1 - (1 - Iqf = 2H i-2q = Vi - 2H 1 - Jì - 2Н q = 2 and squaring this would give the frequency of affected homozygotes. Thus in parts of Africa where the incidence of carriers of sickle cell anaemia (sickle cell trait) has been found to be as high as 1 in 3, 1 - Ji - 0.667 « = 2 = 0.211 and therefore q^ = 0.044 or 1 in 23 Another approach is illustrated by a study (Kellerman et al, 1973) in which the induction of aryl hydrocarbon hydroxylase in human lymphocytes showed a trimodal distribution in the population and it was suggested that the three phenotypes represented the action of two alleles (A and B). Out of a total of 161 individuals investigated the phenotypic frequencies were: low inducibility = 86 {AÄ) intermediate inducibihty = 59 {AB) high inducibility = 16 (BB) , . . 86 1 / 59 \ Therefore A gene frequency = + \161 161 2V161 = 0.717 and В gene frequency = 1 — 0.717 = 0.283 Therefore the expected phenotype frequencies are: = 161 (0.717) (0.717) =82.8 AB = 161 (2) (0.717) (0.283) = 65.3 BB = 161 (0.283) (0.283) = 12.9