Schematic of the wheat karyotype. The wheat karyotype is arranged into genomes A, B, and D and into seven homeologous groups (e.g., group 1 consists of chromosomes 1A, 1B, and 1D). This arrangement is after , who classified homeologous chromosomes based on their ability to compensate for each other’s absence. Examples of the different types of sequences are drawn on top of the chromosomes, namely: group-specific sequences that are present in only one homeologous group, chromosome-specific sequences (CSSs) that are present in only one chromosome pair, genome-specific sequences (GSSs) that can be on more than one chromosome pair but only in one of the genomes, and nonspecific sequences that are present on both homeologous and nonhomeologous chromosomes. The nonspecific sequences are mainly dispersed repeats (adapted from ).