Linkages between Genes for Coat Colour and Resistance to Warfarin in Rattus norvegicus

Abstract

RESISTANCE to warfarin in rats from Wales is inherited as a single autosomal gene with dominant effect^1,2. We now report evidence that the gene belongs to linkage group I (ref. 3). Backcross offspring of rats heterozygous for resistance and two or three coat colour genes are classified in Table 1. The resistance gene is denoted Rw² and its allele for susceptibility Rw¹. Symbols for coat colour genes are those used by Robinson³. The screening test¹ was lethal to only 0.934 of susceptible animals and this was allowed for before analysing the data. Clear evidence of linkage between the c, p and Rw loci is shown (Table 2). The relevant recombination values are: c–Rw 0.2155 ± S.E. 0.0225; p–Rw 0.2667 ± S.E. 0.0361; and p–c 0.1667 ± S.E. 0.0304. The linear order is evidently p–c–Rw, for recombination was more frequent between p and Rw than between the other pairs of loci. Observed double-crossover types numbered 8.6 as against 5.4 expected; the difference is insignificant. The wild-type × albino cross provided a three-point linkage test and gave the map distance between p and Rw as 38.13 ± S.E. 3.97 units as compared with 38.22 ± 3.78 units derived by adding the recombination values given here for the component segments. Our finding of linkages between resistance and coat colour characters is contrary to that of other investigators².