Sex Chromosomes in the Germ Cells of the Chicken, Turkey and Japanese Quail ,

In all the reported cases of the class Aves, it is the male which is the homogametic sex with two Z chromosomes, while the female is heterogametic with one Z and one W chromosome. In the species under study (Gallus domesticus; Meleagris gallopavo; and Coturnix coturnix), the Z is metacentric and is the fourth or fifth largest chromosome in the complement. The W is much smaller (8th to 10th in size) with a median or sub-median centromere. The question of whether the W and Z chromosomes exist singly or in the form of a ZW bivalent during oögenesis is the issue of the present study. The material for oögenesis came from developing ovaries of 1–3 days old chicks or from embryos, 1–2 days prior to hatching. The material for spermatogenesis came from testes of sexually mature males. The material was given 10 minutes hypotonic treatment in 0.45 percent …