An approach to identifying functional groups within the multi-copy <i>var</i> genes.

<p><b>(A)</b> Graphical representation of a stochastic block model for the normalized co-occurrence matrix <b>Z</b>, 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 <i>z</i>-scores between pairs of HB functional groups, which are assumed to be drawn from the same normal distribution. <b>(B)</b> Homology blocks recombine to form <i>var</i> gene sequences, so after homology blocks are classified into functional groups (7 shown here, represented by distinct colors), <i>var</i> functional types can be defined as unique combinations of homology block functional groups (HBFG types). Viewing <i>var</i> sequences as HBFG types reduces diversity by over two orders of magnitude.</p>