all the mackerel tabbies studied had a normal version of a gene the researchers named Taqpep while all the blotched tabbies had a mutated from of the gene.
58 of 58 blotched tabbies had a mutation in each of its two copies of Taqpep.
51 of 51 mackerel tabbies had a least one unmutated version of the Taqpep gene.