CPG ISLANDS OF THE PIG

We describe an analysis of the CpG islands (CGIs) of the pig. We have used both database survey and a porcine genomic library that is enrich ed for CGIs. Approximately half of 41 pig genomic database sequences h ad CGIs with an average G + C content of 65.3%, an average CpG observe d/expected frequency of 0.85, and an average size of 978 bp. Of 27 CGI library clones, 16 were nonrepetitive, nonribosomal DNA and CGI-like. CGI library clones had similar average values for G + C and CpG frequ ency to CGIs of database genes, and an average size of 670 bp, as MseI cuts within some islands. Library clones were also shown to be low co py number and unmethylated in genomic DNA. The presence in the library of seven previously known CGI sequences was confirmed as was the abse nce of one nonisland sequence. The CGI library exhibits an R-band patt ern for many chromosomes in FISH analysis. The pig chromosome arms tha t show the most dense CGI population are homologous to segments of hum an chromosomes that are known to be gene rich.