Variation in the number of alpha-globin loci in sheep.
Southern blot analysis was used to compare sheep and goat restriction-endonuclease maps of the DNA region containing the alpha-globin genes. The identical digestion patterns observed in both species with three endonucleases (BamHI, BstEII, and PstI) show that in sheep a single chromosome normally bears two nonallelic alpha-globin genes positioned at the same distance as in goat. Variant digestion patterns with enzymes that cleave outside (BamHI and HindIII) and within (EcoRI) the alpha-globin loci allowed us to infer that chromosomes with different numbers of alpha-globin loci are also present in sheep. In particular, in the 60 sheep considered, four individuals were heterozygous (alpha alpha/alpha alpha alpha) and one was homozygous (alpha alpha alpha/alpha alpha alpha) for chromosomes with three loci and one individual was heterozygous for a chromosome with four loci (alpha alpha/alpha alpha alpha alpha). This variation in the number of copies of alpha-globin loci can be explained by means of unequal crossovers.
D000818:Animals; D002874:Chromosome Mapping; D004262:DNA Restriction Enzymes; D005796:Genes; D005914:Globins / Q000235:genetics*; D006041:Goats / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D012756:Sheep / Q000235:genetics*
D005914:Globins; D004262:DNA Restriction Enzymes