Of 310 random cosmid clones, 216 were positive for PRE-1 sequences by
Southern hybridization. Thirty nine sub-fragments positive for the PRE
-1 sequences were cloned from independent cosmid clones, and sequenced
, with 17 complete PRE-1 elements found. Seven PRE-1 loci were amplifi
ed by polymerase chain reaction using genomic DNA of 12 unrelated pigs
as template. The amplified fragments were then subjected to an analys
is of single strand conformation polymorphism, with all the loci being
polymorphic.