Crossing over creates heteroduplex DNA

A molecular model of crossing over. Only the two chromatids (blue and red) participating in the crossover are shown. The 3′-to-5′ strand is placed on the inside of both for clarity. The chromatids differ at one site, GC, in one allele (perhaps allele A) and AT in the other (perhaps a). Only the outcome with mispaired heteroduplex DNA and a crossover are shown. The final crossover products are shaded in yellow and blue.