Here's a link and my question relates to the diagram present in the link: http://biology.stackexchange.com/questions/48923/crossing-over-holliday-model
Why is the heteroduplex with constant terminal genes called a non-crossover despite exchange of middle DNA segments?
Heteroduplex called patch does not have double-stranded recombinant regions, there is a new fragment in a single strand only. It means that the two strands are not complementary at that regions and as soon as DNA repair systems detects it, the mistake will be corrected. In case of heteroduplex called splice, there are double-stranded changes, which do not go against the complementarity principle and thus, they will not be removed or corrected in any way.