Human biochemical genetics / by H. Harris.

  • Harris, Harry, 1919-1994.
Date:
1959
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Human biochemical genetics / by H. Harris. Source: Wellcome Collection.

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    i8 ASPECTS OF MENDELIAN HEREDITY Table 2. Random mating table for an autosomal gene pair A and a, where only twophenotypes can be recognised. Phenotype Ä corresponds to genotypes AA and Aa. Phenotype ä corresponds to genotype aa Parents Offspring Frequency r- Mating of mating A ä Ax A р\\+дУ p^-b2p^q Axä lpq\\-\-q) 2pq^ 2pq^ ä X ä q^ — q^ All matings p^ + 2pq q^ types Gm (a + ) and Gm (a — ), and in a random series of 360 healthy Swedish adults they found that 59*7 per cent were Gm(a + ) and 40-3 per cent were Gm (a — ). The observed distribution of the two types among the progeny of the different types of mating occurring in twenty-eight families is shown in Table 3. Gm (a —) x Gm (a — ) matings resulted only in Gm (a — ) offspring. This suggests that Gm (a — ) is inherited as a recessive character. If this is so, the gene frequency of the gene Gm for which Gm (a — ) individuals are homo¬ zygous will be in this Swedish population 0-635, that is, VO-403, and the frequency of the other allele Gm^ will be 0-365, that is, 1 —0-635. From these gene frequencies the expected numbers of matings of the different types and the expected numbers of the two phenotypes among their progeny may be readily calculated. It will be seen that the agreement between the observed numbers and those theoretically expected is very good. Table 3. y-Globulin types {Gm (a + ) and Gm {a — )) in twenty-eight families. (After Grubb and Laurell, 1956) Parents Children Rare abnormalities One important conclusion which follows from the Hardy-Weinberg principle concerns the frequencies with which heterozygotes and homozygotes for a relatively rare gene may be expected to occur in a given population. The point is illustrated in Table 4, from which it can be seen that when the gene a is relatively uncommon, the