Phylogenetic analysis of B6 Mup loci. This unrooted tree was constructed using intron 2, which has an average size of 766.9 bp. Nodes with a bootstrap support of less than 700/1,000 replicates are marked with an asterisk, with the exception of those nodes within the clades marked 'A' and 'B' which are, in general, poorly supported. Numbers and letters at each node refer to genes and pseudogenes, respectively, as annotated in Figure 1a. Pseudogenes O and P are not present as these partial loci do not contain an adequate portion of intron 2; similar phylogenetic analysis with different sequence indicates that these pseudogenes also form isolated nodes (data not shown).