Additional linkage relationships within the Z chromosome of the chicken

Genetic linkage tests were conducted using four Z-linked loci and three Z-linked chromosome rearrangements (interchanges). Z-linked recessive white skin (y) segregated independently from the Z-linked barring (B) and silver (S) loci. A map distance of 18.2 +/- 3.2 was found between y and the MN t(Z;1) interchange. A previous report had shown that B was located 22 map units from this interchange, therefore, because B and y were found not to show measurable recombination, the linear order is B-interchange-y. The MN t(Z;3) interchange was tested against S, and no recombinants were recovered in 217 backcross progeny, indicating very close genetic linkage. The NM 7659 t(Z;1) interchange was tested against the dermal melanin locus (id+) and independent assortment was noted. This supports other work that has shown that the S and id+ loci lie on opposite arms of the Z chromosome. Evidence is reviewed that supports the concept that S and the NM 7659 and MN t(Z;3) interchange break points are located on the short arm, while B, id+, y, and the MN t(Z;1) interchange break point are located on the long arm of the Z chromosome.