MC4R and obesity due to melanocortin 4 receptor deficiency: As expected, pairwise LD measures between the two non-synonymous MC4R polymorphisms and the two SNPs of the obesity haplotype are larger for D′ (range 0.475–1), whereas the respective r2 values were low (range 0.001–0.007) due to the low allele frequencies of these polymorphisms.