An approach to identifying functional groups within the multi-copy var genes.
(A) Graphical representation of a stochastic block model for the normalized co-occurrence matrix Z, for nine homology blocks divided into three functional groups (HB functional groups 1–3). The blocks within the matrix of a single color represent the z-scores between pairs of HB functional groups, which are assumed to be drawn from the same normal distribution. (B) Homology blocks recombine to form var gene sequences, so after homology blocks are classified into functional groups (7 shown here, represented by distinct colors), var functional types can be defined as unique combinations of homology block functional groups (HBFG types). Viewing var sequences as HBFG types reduces diversity by over two orders of magnitude.