The organization of the k+ and K alleles. The k+ allele contains two genes; PRLR (purple exons) and SPEF2 (black exons). The K allele contains the original genes and the two partial duplicate genes, dPRLR and SPEF2. The green box indicates the unoccupied ev21 integration site. One of the red boxes indicates an unoccupied and the other an occupied ev21 integration site. The large yellow and blue boxes indicate the 176.3 kb duplicated block. The grey arrows indicate transcriptional start and stop. The question mark indicates a transcript of unknown length.