Figure 1. Alternative resolutions of a Holliday junction. Following the formation of a Holliday junction, resolution can result in gene conversion with or without associated crossover. Under Holliday's original model, all gene conversion results from mismatch repair of heteroduplex.

Figure 2. The double-strand break model of meiotic recombination. Following a double-strand break, 5¢ ends are digested, allowing single-stranded 3¢ tails to invade homologous sequences. Resynthesis of the gap generated by the exonucleolytic activity results in the formation of an intermediate containing two Holliday junctions. This structure is capable of generating a heteroduplex via branch migration through homologous sequences. Resolution of this intermediate can result in gene conversion with or without associated crossover. Gene conversion results from gap resynthesis and mismatch repair of heteroduplexes.

Figure 3. Gene conversion between paralogous sequences can appear to have occurred as a result of a double crossover between misaligned chromatids (or chromosomes). This process generates two reciprocal products; however, after segregation, only one product may be observed. Two independent instances of the upper product have been observed, but no examples of the bracketed, lower, product. Crossovers are shown as being restricted to minimum efficient processing segments of greater than 200 bp of sequence identity between the repeats.