The validity of genetic models underlying quantitative traits

This paper reviews the validity of the assumptions and predictions of genet ic models used for the analysis of quantitative traits. When data on phenot ypes and pedigrees but not individual genes are available, the traditional, additive, infinitesimal model makes satisfactory predictions of short-term response to selection despite the incorrectness of its assumptions. Improv ements can made in the model such as the inclusion of non-additive variance components or major genes but gains in the accuracy of prediction have sel dom been demonstrated. When data are available on individual genes or marke rs, two models are in common use - a two allele and an infinite allele mode l. The two models differ in a number of respects such as assumptions about segregation variance, estimation of fixed or random effects and number of p arameters to be estimated when multiple traits are used. There is little in formation on the accuracy with which either model predicts the performance of future animals. (C) 2001 Elsevier Science B.V. All rights reserved.