In order to construct a chicken (Gallus gallus) cytogenetic map, we isolated 134 genomic DNA clones as new cytogenetic markers from a chicken cosmid DNA library, and mapped these clones to chicken chromosomes by fluorescence in situ hybridization. Forty-five and 89 out of 134 clones were localized to macrochromosomes and microchromosomes, respectively. The 45 clones, which localized to chicken macrochromosomes (Chromosomes 1–8 and the Z chromosome) were used for comparative mapping of Japanese quail (Coturnix japonica). The chromosome locations of the DNA clones and their gene orders in Japanese quail were quite similar to those of chicken, while Japanese quail differed from chicken in chromosomes 1, 2, 4 and 8. We specified the breakpoints of pericentric inversions in chromosomes 1 and 2 by adding mapping data of 13 functional genes using chicken cDNA clones. The presence of a pericentric inversion was also confirmed in chromosome 8. We speculate that more than two rearrangements are contained in the centromeric region of chromosome 4. All 30 clones that mapped to chicken microchromosomes also localized to Japanese quail microchromosomes, suggesting that chromosome homology is highly conserved between chicken and Japanese quail and that few chromosome rearrangements occurred in the evolution of the two species.

Using direct R-banding fluorescence in situ hybridization, we determined the location of 31 functional genes on chicken chromosomes. Replication R-banded chromosomes were obtained by synchronizing splenocyte cultures with excessive thymidine, followed by BrdU treatment. Thirty-one functional genes were directly localized to banded chicken chromosomes using genomic DNA and cDNA fragments as probes. The possibility of conserved linkage homology between chicken and human chromosomes was demonstrated for seven chicken chromosome regions (1p, 1q, 2q, 4p, 4q, and 5q).