Linkage disequilibrium between NAT1 and NAT2 SNPs in Black and Mixed Ancestry South Africans. Plots show r2 and D’ values for pairwise LD between NAT1 and NAT2 variants in the South African Black and Mixed Ancestry population groups. The left triangle in each plot represents NAT1 SNPs, while the right triangle represents NAT2 SNPs. Colour intensity of squares (black to white) indicates the strength of LD (high to low) by D’, while numbers within squares refer to r2 values for pairwise SNPs. D’ and r2 refer to different statistical methods to measure linkage disequilibrium between alleles; r2 is preferred to predict one allele given the other, whereas D’ is mainly used to assess recombination patterns such as haplotype blocks. Linkage disequilibrium analysis was carried out in control groups by using Haploview .