Long-term selection by asymmetric trait distribution

A quantitative trait is assumed to be genetically affected by a polygenic e ffect and a major effect of a single dialellic locus. Such a model is calle d mixed model of inheritance and the identified gene is denoted as quantita tive trait locus (QTL). By choosing the part of the QTL-variance, the degre e of dominance and the Frequency of the favourable allele it is possible to generate distributions with given level of asymmetry characterised by skew ness and kurtosis. If the ratio of QTL- and phenotypic variance is small (l ess than 8%), then genotype-environment interaction can be used in the mixe d inheritance model to explain values of skewness and kurtosis estimated wi th poultry data. The situation is considered where the environmental varian ces given for the three QTL-genotypes show a wide range. In most of these c ases the short- and long-term selection does not effects the high values fo r skewness and kurtosis over multiple generations. Further the ratio of res ponse to selection and the difference of selection depends on the selection intensity.