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 effect1,2. 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.