Heteroduplex

A heteroduplex is a double-stranded (duplex) molecule of nucleic acid originated through the genetic recombination of single complementary strands derived from different sources, such as from different homologous chromosomes or even from different organisms.

By one pathway, a structure called a double Holliday junction (DHJ) is formed, leading to the exchange of DNA strands.

In meiosis, the process of crossing-over occurs between non-sister chromatids, which results in new allelic combinations in the gametes.

In crossing-over, a Spo11 enzyme makes staggered nicks in a pair of sister chromatid strands (in a tetrad organization of prophase).

This process can yield double Holliday junctions that when cut in a transversal pattern by endonucleases form 2 heteroduplex strand products.

A current model of meiotic recombination, initiated by a double-strand break or gap, followed by pairing with a homologous chromosome and strand invasion to initiate the recombinational repair process. Repair of the gap can lead to crossover (CO) or non-crossover (NCO) of the flanking regions. CO recombination is thought to occur by the Double Holliday Junction (DHJ) model, illustrated on the right, above. NCO recombinants are thought to occur primarily by the Synthesis Dependent Strand Annealing (SDSA) model, illustrated on the left, above. Most recombination events appear to be the SDSA type. At various steps of the recombination process, heteroduplex DNA (double-stranded DNA consisting of single strands from each of the two homologous chromosomes) is formed.