A panel of 27 pig × rodent somatic cell hybrids was produced and characterized cytogenetically. The first step of this study consisted of hybridizing a SINE probe to GTG-banded metaphases of each hybrid clone in order to count and identify the normal pig chromosomes and to detect rearranged ones. The second step consisted of using the DNA of each clone as a probe after pIRS-PCR (porcine interspersed repetitive sequence-polymerase chain reaction) amplification to highly enrich it in pig sequences. These probes, hybridized to normal pig metaphase chromosomes, enabled the identification of the complete porcine complement in the hybrid lines. Whole chromosomes and fragments were characterized quickly and precisely, and results were compared. In addition to this cytogenetic characterization, molecular verification was also carried out by using primers specific to six microsatellites and to one gene previously mapped to pig chromosomes. The results obtained allow us to conclude that we have produced a panel that is informative for all porcine chromosomes. This panel constitutes a highly efficient tool to establish not only assignments of genes and markers but also regional localizations on pig chromosomes.

A cell synchronization technique allowed the high-resolution GTG-banding pattern of rabbit chromosomes to be determined. A karyotype of the late-prophase 622-band stage is presented.

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A high-resolution GTG-banded karyotype of the pig was obtained after methotrexate-induced cell synchronization. A diagrammatic representation of the banding pattern at the 539-band level is presented.

A review of the present status of the porcine gene map is given with references. A total of 84 loci have now been studied, and genes have been assigned to 17 chromosomes. Among them, six chromosomes are defined by only one marker. No loci have been attributed yet to three chromosomes.