In a population in equilibrium consisting of homozygous dominants, heterozygous dominants and recessives the last named class comprises 2.8% of the total: assuming that a 10% selection rate now operates in its favour as opposed to the two classes of dominants--in how many generations will the recessive come to constitute one-quarter of the population? The answer is to be looked for in column B (since the favoured variety is recessive) under the fraction 100/90. The recessive passes from 2.8% to 11.1% of the population in 36 generations, and from 11.1% to 25% in a further 16 generations--_i.e._ under a 10% selection rate in its favour the proportion of the recessive rises from 2.8% to 25% in 52 generations. {155} A: Where the new variety is dominant +-----------+-----------+----------+------------------------------------+ | | | | Number of generations taken | |Percentage |Percentage |Percentage| to pass from one position | |of total |of total |of total | to another as indicated | |population |population |population| in the percentages of different | |formed by |formed by |formed by | individuals in left-hand column. | |old variety|the hybrids|the new +--------+--------+--------+---------+ | | |variety | 100/50 | 100/75 | 100/90 | 100/99 | +-----------+-----------+----------+--------+--------+--------+---------+ | 99.9 | .09 | .000 | | | | | | 98.0 | 1.96 | .008 | 4 | 10 | 28 | 300 | | 90.7 | 9.0 | .03 | 2 | 5 | 15 | 165 | | 69.0 | 27.7 | 2.8 | 2 | 4 | 14 | 153 | | 44.4 | 44.4 | 11.1 | 2 | 4 | 12 | 121 | | 25. | 50. | 25. | 2 | 4 | 12 | 119 | | 11.1 | 44.4 | 44.4 | 4 | 8 | 18 | 171 | | 2.8 | 27.7 | 69.0 | 10 | 17 | 40 | 393 | | .03 | 9.0 | 90.7 | 36 | 68 | 166 | 1632 | | .008 | 1.96 | 98.0 | 170 | 333 | 827 | 8243 | | .000 | .09 | 99.9 | 3840 | 7653 | 19,111 | 191,002 | +-----------+-----------+----------+--------+--------+--------+---------+