Robin Holliday proposed the junction structure that now bears his name as part of his model of homologous recombination in 1964, based on his research on the organisms "Ustilago maydis" and "Saccharomyces cerevisiae." The model provided a molecular mechanism that explained both gene conversion and chromosomal crossover. Holliday realized that the proposed pathway would create heteroduplex DNA segments with base mismatches between different versions of a single gene. He predicted that the cell would have a mechanism for mismatch repair, which was later discovered. Prior to Holliday's model, the accepted model involved a copy-choice mechanism where the new strand is synthesized directly from parts of the different parent strands.