Cluster choices. Nodes on neighboring markers l and l + 1 (shaded) that form a cluster. Large node represents the genotype of an individual, a small node the meiosis indicator an individual. In the CVM approximation, only marginals of clusters on the marker loci are computed. A shows cluster choice C1. Genotype nodes of parents and children and meiosis nodes of children in the nuclear family of adjacent marker loci form a single cluster. B shows cluster choice C2. Genotype nodes of parents and children and meiosis nodes of children in a nuclear family on one marker locus form a cluster. The meiosis nodes of the children form a separate cluster.