Minimum mutation networks of the TNF haplotypes. (a) The Gambian and (b) the Malawian population. Each circle represents a haplotype, and the size of the circle is proportional to the haplotype frequency. Each connecting line corresponds to a mutational event, and the position of the resulting SNP is indicated in base pairs from the transcriptional start of the gene. Broken lines indicate recombination. The numbers correspond to the haplotype indentifiers listed in Table 2. Filled circles represent haplotypes that were not found in that population. The haplotype labelled 'P' was found in two chimpanzees, a gorilla, and two orang utans. Haplotypes of frequency less than 1% are not shown.