Figure 4.

Representative Southern blot hybridization showing the presence of the Belgian Blue and Piedmontese mutant sequences only in double-muscled breeds of cattle. Exon 3 PCR products were hybridized to oligonucleotide probes spanning the wild-type sequence of the region of the Belgian Blue mutation (top row), the Belgian Blue mutation Δ937–947 (second row), the wild-type sequence at nucleotide 1,056 (third row), and the Piedmontese mutant sequence at nucleotide 1,056 (bottom row). Differences in band intensity reflect differences in amounts of PCR products loaded, as judged by ethidium bromide staining (data not shown). Homozygosity for the mutations was seen only in double-muscled cattle and not in any conventional cattle as described in the text (P < 0.001 by χ²).