Restriction fragment length polymorphism in sheep at the growth hormone locus is the result of variation in gene number

DNA samples from 70 sheep of the Awassi, Assaf, Booroola Merino and German Mutton Merino breeds, of the Booroola Merino X Awassi and Booroola Merino X Assaf crosses, of three wild sheep, and of seven Saanen goats, were digested with the restriction enzymes BamHI, EcoRI and HindIII, and screened for restriction fragment length polymorphism (RFLP) using the bovine growth hormone (GH) gene as a probe. This and further analysis of selected DNA samples with 6 additional restriction enzymes (EcoRV, PstI, PvuII, RsaI, SacI and TaqI) revealed RFLP's that is probably due to the presence of two alleles at the GH locus; A predominant allele (Gh2), in which the growth hormone gene is duplicated and the two copies are located at a distance of 3.5 Kb apart, and a rare allele (Gh1), in which the growth hormone gene is present as a single copy. The results also indicate that while the 5’ flanking regions of the two GH copies of the Gh2 allele are different, the 3’ flanking region appears to be conserved.