Figure 2.

Illustration of the procedure to make the haplotype graph G₁ connected. Solid circles indicate observed haplotypes from sequencing in sequence space. Observed haplotypes are grouped in three connected components denoted with uppercase letters in boldface type, A, B, and C. The shortest mutational path between any pair of connected components is indicated with lines and labeled with lowercase italic letters a, b, and c. Blue solid circles indicate those haplotypes forming the endpoints of the shortest path between any pair of connected components. The aim is to make the whole graph connected while inserting the least number of unobserved haplotypes. In this case, the two paths a and b require inserting only two unobserved haplotypes each, while path c requires inserting eight haplotypes and is not used. The edges a and b form the minimum spanning tree of connected components and the haplotypes representing the solid circles are inserted.