Whole genome radiation hybrid mapping

Whole genome radiation hybrid (WG-RH) mapping has come of age with the recent publication of two WG-RH maps of the human genome. The two different approaches demonstrate the emergence of WG-RHs as stand-alone mapping tools. The technology for generating physical maps using irradiation and fusion gene transfer (IFGT) was first developed by Goss and Harris, who demonstrated that fragments of genomic DNA from a lethally irradiated diploid human cell line could be rescued by cell fusion with a recipient rodent cell line. This technique was generally under-exploited, but was used for mapping human X chromosome genes. It was not until 15 years later, when Cox et al. used radiation hybrids for the construction of a high resolution map of chromosome 21, that the method became widely used for mapping individual mammalian chromosomes. These maps were constructed using hybrids generated by IFGT between a donor somatic cell hybrid containing a single human chromosome and the recipient rodent cell line. Mapping the entire human genome using this approach is impractical, because a panel of 100-200 hybrids per chromosome would require screening over 4000 hybrids to generate a genomic map. WG-RH mapping was revived by Walter et al., who reverted to the original method of Goss and Harris to demonstrate that a panel of hybrids, generated by IFGT of a diploid human cell line with a rodent recipient line, could be used to map any human chromosome. Using a panel of 44 WG-RHs, an ordered map of the long arm of chromosome 14 was generated containing 40 markers, with five gaps in the map. These data suggested that a single panel of 100 hybrids could be used to generate a WG-RH map. The additional hybrids are needed to provide the high resolution necessary for the generation of maps containing over 10000 markers. Integrated physical and radiation hybrid mapping. Radiation hybrid (RH) panels have been successfully used in the generation of genetically anchored YAC (yeast artificial chromosome) and cosmid contigs across the human genome. Monaco et al. mapped RHs to X chromosome cosmid and YAC libraries, by direct hybridization of Alu PCR products of individual hybrids to library clones, gridded on nitrocellulose membranes. Kumlien et al. used the same method to hybridize eight RHs containing fragments of chromosome 21, establishing preliminary map positions for chromosome 21 YACs along subregions of the chromosome. Employing the same technique, 72 X chromosome RHs were used to map 1