A GENETIC-MAP OF QUANTITATIVE TRAIT LOCI FOR BODY-WEIGHT IN THE MOUSE

The genetic basis of body weight in the mouse was investigated by meas uring frequency changes of microsatellite marker alleles in lines dive rgently selected for body weight from a base population of a cross bet ween two inbred strains. In several regions of the genome, sharp peaks of frequency change at linked markers were detected, which suggested the presence of single genes of moderate effect, although in several o ther regions, significant frequency changes occurred over large portio ns of chromosomes. A method based on maximum likelihood was used to in fer effects and map positions of quantitative trait loci (QTLs) based on genotype frequencies at one or more marker loci. Eleven QTLs with e ffects in the range 0.17-0.28 phenotypic standard deviations were dete cted; but under an additive model, these did not fully account for the observed selection response. Tests for the presence of more than one QTL in regions where there were large changes of marker allele frequen cy were mostly inconclusive.