Relative positions of the loci of the peacomb (P), eumelanin restrictor (Db), eumelanin extension (Ml) and plumage pattern (Pg) genes of the domestic fowl.

A single comb Partridge Wyandotte bantam male was mated with two Indian Game bantam females to produce a double heterozygote of the linked eumelanin extension (Ml) and pea comb (P) genes. Four females so produced were mated with their sire to provide a backcross to the double recessive. Forty crossovers occurred among the 86 progeny suggesting linkage of approximately 46 units between Ml and P. The eumelanin restrictor gene (Db) had previously been shown to be linked with P, Ml and Pg by approximately 28, 10 and 17 units respectively and, furthermore, the locus of Ml had been shown to lie between the loci of Db and Pg. The locus of Db appears therefore to lie between the loci of P and Ml and hence the relative positions of the loci of the 4 genes is P, Db, Ml, Pg.