This transgene consists of a modified mouse BAC clone RP23-274L11 which contains the entire Kit locus. The Kit locus in the BAC was modified by the insertion of a floxed stop cassette into intron 1 and the insertion of an A to T point mutation in exon 17 resulting in an aspartic acid to valine mutation at position 814. This mutation is homologous to the D816V mutation in humans. This line carries 5 - 6 copies of the transgene.