SIZE OF BREEDING POPULATIONS REQUIRED FOR SELECTION PROGRAMS

The minimum population size required for selection in order to reduce the effect of genetic drift to a particular level has been considered. The model of Nicholas was extended to include the measurement-error v ariance in the response variance. Situations where the sex ratios amon g scored and breeding individuals are unequal are also considered. Whe n the duration of a selection experiment is relatively long, Nicholas' approximation (i.e., assuming that measurement error is negligible re lative to drift) is useful in determining the minimum effective popula tion size required. However, the measurement-error variance becomes an important source of variation in short-term (less than or equal to 5 generations) selection experiments, and should not be ignored.