Growth hormone restriction fragment length polymorphisms that segregate with 42-day live weight of mice

The known correlation between growth hormone levels and growth rate in a number of species prompted us to examine if polymorphic restriction fragment alleles at the growth hormone locus in mice might be associated with differentiable rates of growth. An F2 population of mice was generated from crosses between a line selected for high 42-day weight and an unselected control line. The original selected and control lines exhibited mean 42-day weights of 30.6 +/- 3.8 and 20.5 +/- 2.6 g, respectively. Since the two lines also differed with respect to the restriction fragments detected by hybridization to a rat growth hormone cDNA probe, an analysis of the F2 generation was carried out to determine whether this polymorphism could be considered a quantitative trait locus for 42-day weight. The results of the analysis indicated that a polymorphic HindIII restriction fragment was correlated (P less than 0.05) with 42-day weight. However, the allele that was positively correlated with weight was the one that was fixed in the original control line, rather than the one from the selected line. While these findings support the potential use of restriction fragment length polymorphisms in quantitative trait evaluation of livestock, they also emphasize the requirement for testing such potential quantitative trait loci in the appropriate genetic background.