W C Wong, W J Boylan
1970 Genetics  
HE effectiveness of recurrent mass selection to change the mean performance Tof a quantitative trait has been shown in many experiments. Notable examples in laboratory animals are reported by MACARTHUR (1949) and by FALCONER (1953) on selection for body size in mice; MATHER and HARRISON (1949) and ROBERTSON and REEVE (1952) on traits in Drosophila; TANAKA, SUZUKI and TAKASAKI (1958) on size in the silkworm and more recently, selection experiments in Tribolium cmtaneum (the flour beetle) by
more » ... ETT, BELL and ANDERSON (1966) and by ENFIELD, COMSTOCK and BRASKERUD (1966) and on growth in mice by RAHNEFELD et al. (1963) . In general, studies of responses to selection have been limited to evaluating the impact of the selection on the same population as that in which selection has been employed. The recently greater utilization of crossbreeding in the livestock and poultry industries has capitalized on heterosis and has resulted in more attention being focused by animal breeders on the effects of intrapopulation selection on the performance of crossbreds when populations are crossed. Generally, in practice, animal breeders select on an intrapopulation basis-i.e., selection is based on performance within the population. Producers of crossbred livestock then must rely on genetic improvement within the purebreds for any genetic improvement in crossbreds. Few experimental data have been published which relate directly to this issue in animals. Pertinent evidence on this topic was reported by RAHNE-FELD, BOYLAN and COMSTOCK (1961) . It should be noted that the paper by RAHNEFELD et al. (1963) is part of that experiment. The primary objectives of this experiment were to evaluate the response to intrapopulation selection in a population in which selection was employed and also the impact 4f that selection in crossbreds when the population was crossed with another. Data obtained from the experiment also provided a basis for evaluating quantitative genetic theory relating to intrapopulation selection and crossbreeding. MATERIALS AND METHODS The data reported here are from an experiment in which mass selection for a single trait was employed in a genetically segregating population. The response to selection was evaluated in the population in which the selection was practiced and also by changes in the mean performance of crossbreds when that population was crossed with another. The single trait on which selection
doi:10.1093/genetics/64.1.69 fatcat:hdgp473kijdp3na4meuwaiszly