On the genetics of rosette pattern in guinea pigs

Summary New data on the heredity of rosette pattern in guinea pigs and a critical review of the data ofPictet andFerrero support the conclusions reached in 1916 on the genetics of the major variations of this character.The results ofPictet andFerrero fully confirm the existence of the primary pair of alleles R, r and are so treated by them in their more recent papers. There is strong evidence that the rough inhibiting factor M (of wild species ofCavia and of many guinea pigs) was present in their stock, in certain smooths which transmitted roughness (R-MM) and in the types described as lisses à crête and monorosettes (R-Mm) but was not recognized. This gene was clearly much less common than in my stocks.Their stocks on the other hand seem to have exhibited more variability in the high grades of roughness and to have reached somewhat higher grades than I have observed. They attribute these variations to two new pairs of genes G, g and D, d, the former said to distinguish two patterns on the trunk, the latter, grades of roughness of the head. The data as presented, contain contradictions in both cases. Nevertheless they indicate segregation in their stock of a pair of alleles distinguishing the highest grade of fancier's rough (RRmmGG), from ordinary high grades (RRmmgg). The contradictions may perhaps be due to overlap. No judgment of the validity of genes D, d can be reached without presentation of data showing the breeding results for trunk and head rosettes simultaneously.