Single Strand Invasion and Chi Sites

A major question is how the homologous sequences of DNA actually find and recognize each other. Remember that we are not talking about two single strands of DNA base-pairing but about the merger of two separate double helixes of DNA in which the bases are turned inwards. The approach seems to differ somewhat between bacteria and higher organisms.

In bacteria, the major proposed mechanism is single-strand invasion. This requires a single-stranded region to form in one of the DNA double helixes. This single strand patch recombinant DNA double helix with a short patch of heteroduplex due to transient formation of a crossover resolution Cleavage of the junction where two DNA molecules are fused together so releasing two separate DNA molecules. Refers to the breakdown both of crossovers formed during recombination and of cointegrates formed by transposition resolvase Enzyme that carries out resolution of DNA

Two homologous molecules of DNA

Two homologous molecules of DNA

Break and join single strand

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