Computer simulation of within family selection in finite populations

The relative efficiency, in terms of selection limits, between mass selection and within family selection was compared by computer simulation methods. A 20-locus additive model was used to simulate a quantitative trait under selection. It was assumed that 50-75 percent of the genetic variance in the base population was controlled by four major genes initially at low frequencies.In populations of size N=100 no loss of major genes was found when either method of selection was used. When N=50 within family selection was generally superior to mass selection but when N=10 the situation was reversed. For N=30 within family selection was more efficient only under high selection intensity or high heritability situations.