Pedigrees show when genes are identical by descent

(a) Pedigree for a half-sib mating drawn in the standard format. Small colored balls represent a single copy of a gene. Within individual A, the pink and blue copies represent the copies of the gene that she inherited from her mother and father, respectively. (b) Pedigree for a half-sib mating drawn in the simplified format used for the analysis of inbreeding. Only lines connecting parent to offspring are drawn, and only individuals in the “closed inbreeding loop” are included. w, x, y and z are symbols for the allele transmitted from parent to offspring.