Inheritance of Scottish-type resistance to warfarin in the Norway rat

Abstract

SUMMARY The inheritance of resistance to the rodenticide, warfarin, in the Norway rat, Rattus norvegicus , derived from a wild rat population in Scotland was studied in the backcross, intercross and testcross. The resistance was found to be due to a major gene with about the same map position in Linkage Group I as the warfarin-resistance gene, Rw 2 , which occurs in the wild rat population in Wales. In heterozygotes, the Scottish resistance gene, unlike the Welsh gene, is incompletely penetrant in expression, though the penetrance was found to increase markedly in response to selection. Differences between the Scottish and Welsh types of resistance suggest that the two resistance genes are allelic.