The Linkage of Polydactyly with Multiple Spurs and Duplex Comb in the Fowl

Abstract

Polydactyly was found to be linked with multiple spurs and with duplex comb. The arrangement of these genes and the approximate crossover distances separating them are: D 28 M 33 Po. The amount of crossing over measured between D and Po was 42 per cent. and there were 9.3 per cent. double cross overs. These determinations were made in backcross populations showing a normal 1 : 1 ratio of polydactylous to four-toed birds. It is shown that interpretation of linkage tests with Po is difficult when, as frequently happens, inhibiting genes prevent the manifestation of polydactyly in heterozygotes. Genes suppressing this mutation seem also to suppress multiple spurs. A summary is given of published evidence and new data showing that D and Po, at opposite extremes of this linkage group, are apparently independent of four other autosomal linkage groups and of seven other genes with which both have been tested.