Karyotype of chicken-pheasant hybrids

The karyotype of the Gallus gallus x Phasianus colchicus mongolicus hybrid was studied in mitoses obtained from peripheral blood leucocytes cultures. The culture method provided high numbers of well spread metaphase chromosomes, without overlapping and suitable for chromosome counts. The modal diploid number of chromosomes found was 78, the same as in the chicken. The hybrid constitution was confirmed by the presence of a macrochromosomal set derived from each parental species, the chicken and the pheasant. In particular, the hybrid origin of metaphases was easily determined by the morphology of two pairs of homologous chromosomes, numbers 2 and 4. The nucleolar organiser regions (NOR) encoding the 18S-5.8S-28S ribosomal DNA, were detected by the silver nitrate staining in one pair of chromosomes, as in the chicken.