Educability-and-Group-Differences-1973-by-Arthur-Robert-Jensen

218 Educability and Group Differences
variance would remain unchanged. Consequently there would be
an increase in VJVp = h2.
9. An allele is one of two (or more) alternative forms of a gene, occupying
the same locus in paired chromosomes.
10. Assuming two kinds of alleles in the population, A and a, only one
of which increases the trait, the distribution of all possible combinations
resulting under random mating is given by the binomial
expansion of (pA+qa)2n, where p and q are the proportions of A
and a alleles in the population and p+q = 1, and n is the number
of gene loci (i.e., gene pairs having the same locus on homologous
chromosomes). The larger the number of gene loci (n) involved
in the trait, the greater must be the disparity from p = q — 0-5 to
produce a given deviation of the distribution from normality and
to produce skewness of the distribution. The number of gene loci
involved in intelligence is not known, but various hypotheses have
put it in the range from 10 to 100. Jinks and Fulker (1970, p. 343)
estimate that at least 22 and perhaps as many as 100 or more
genes are involved in determining individual differences in IQ.
11. A detailed account of the quantitative genetics of assortative mating
is provided by Crow and Felsenstein (1968).