Genomic references are structured as a reference graph that represents diploid genotypes in organisms. A path through a series of connected nodes and edges represents a genetic sequence. Genetic variation within a diploid organism is represented by multiple paths through the reference graph. The graph may be transformed into a traversal graph in which a path represents a diploid genotype. Genetic analysis using the traversal graph allows an organism's diploid genotype to be elucidated, e.g., by mapping sequence reads to the reference graph and scoring paths in the traversal graph based on the mapping to determine the path through the traversal graph that best fits the sequence reads.