Chromosomal clustering of five defined endogenous retrovirus loci in White Leghorn chickens.

By using in situ hybridization, we localized three endogenous chicken retrovirus loci associated with the gs- chf- phenotype to distinct regions on chromosome 1. These three loci, ev4, ev5, and ev8, along with the two other known gs- chf--associated loci in White Leghorn chickens, ev1 and ev13, appear to be evenly distributed along chromosome 1, occurring approximately every 1.8 X 10(7) base pairs. The presence of all five loci on chromosome 1 represents a highly nonrandom distribution and all but eliminates a mechanism of independent random integration events for the generation of these loci.