Time of detection of recessive genes: effects of system of mating and number of examined individuals.

The elapsed time from the appearance of a single copy of a recessive gene in a population with separate sexes until the first detection of a recessive homozygote has been analyzed using simulation techniques. Several systems of mating frequently used in laboratory maintenance and artificial selection processes have been the subject of this study. The expected time of detection (T) in each system of mating is described by a function of number of parents (N) and the factor K that when multiplied by N gives the number of examined individuals per generation (e.g. T=1.6+1.8 (N/K) (1/3) for the mass-mating system). Although the expected time of detection changes greatly depending on the system of mating and on the K value (the causes are discussed), both the time scale (N (1/3)) and the coefficient of variation of the distribution of the times of detection (2/3) seem to be unaffected. The additional reduction of the effective population number caused by artificial selection on a heritable trait modifies the expected detection time in a minor way unless both high heritability and high selection intensity are involved.