Abstract
A bovine 5,000 rad WG-RH panel was used to construct an RH map of bovine chromosome 5 (BTA5). Twenty-one microsatellites and thirteen genes were scored in the panel using PAGE and radioactive labeling. Marker retention ranged from 8.9%-25.8% and averaged 17.8%. Pairwise locus analysis placed all markers in a single syntenic group with a LOD support of 4.0. At a LOD support of 8.0, a centromeric group of 23 syntenic markers was formed. Telomeric groups of 11 and 9 markers were assembled with a LOD support of 6.0 and 8.0, respectively. All markers were ordered by maximum likelihood methods using the program RHMAP. Only 13 markers were ordered with a LOD support of at least 3.0, while 25 and 29 markers were ordered with a support of at least 2.0 and 1.0, respectively. Total length of the comprehensive RH map was 435.9 cR5,000, with an average marker separation of 12.8 cR5,000. The largest gaps in the map were 55.0 and 30.4 cR5,000 in length. The locus orders of markers common to both the RH map and the USDA-MARC linkage map were identical. The relationship between the RH and linkage maps was calculated to be 3.74 cR5,000/cM.
Highlights
Radiation hybrid (RH) mapping is a modification of the somatic cell hybrid mapping technique that can resolve the location of genes to very small chromosomal segments
Twenty-one microsatellite markers and 13 genes with known human homologs were scored on the bovine radiation hybrid panel (RHA) panel
Of the 90 hybrid lines in the RHA panel, 52.2% were informative for the scored markers, 45.6% retained none of the markers, and 2 hybrids retained all of the scored markers, one had one untyped
Summary
Radiation hybrid (RH) mapping is a modification of the somatic cell hybrid mapping technique that can resolve the location of genes to very small chromosomal segments. In contrast to linkage mapping, RH mapping does not depend on the intraspecies polymorphism of markers or their segregation within a pedigree structure to map genes, but is based on the random retention of unselected donor genome fragments as insertions, translocations, and/or microchromosomes within hybrid cell lines. Distance within a RH map is measured in centiRays (cR) and depends on the radiation dosage used to fragment the donor genome. Ers, for example, corresponds to a 1% frequency of breakage between the markers within the hybrid cell line panel, after exposure of the donor genome to an X-radiation dosage of 5,000 rads (McCarthy et al, 1997). Because the frequency of breakage can be made high according to the radiation dosage applied, whole-genome RH mapping can produce high-resolution maps using a relatively small number of cell lines. For a linkage mapping study to obtain a similar resolution, a very large mapping population would be required
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