Index >> Bacterial Recombination >> Models Of The Molecular Basis Of Generalised Recombination

Models Of The Molecular Basis Of Generalised Recombination - The essential features of recombination are breakage and reunion of DNA. In prokaryotes reunion takes place by the formation of a heteroduplex joint. This is a form of molecular splicing in which each parent contributes one strand. One of the assumptions of recombina­tion is that homologous dsDNA molecules do not attract each other at specific points, i.e. there are no obvious forces of pairing. Another assumption is that hydrogen bond pairing between complementary regions of ssDNA is involved in recognition. 

B. Exchange of strands between the two duplexes takes place a cross bridge.

C. The cross-bridge can diffuse by a zipper-like action (branch migration). Equivalent bases of the two original molecules exchange places.

D. Additional nuclease cut remove the cross-bridges. The subsequent gaps are closed by DNA polymerase and ligase action. The net result is double exchanges in two progeny strands and no exchange in two.

E. The parental strands can undergo 'isomerization' in which a steric rearrangement converts the bridging pair of strands into outside strands and vice versa.

F. Removal of cross-bridges by nuclease cuts and gap closure by DNA polymerase and ligase (as in D) results in single exchanges in all four progeny strands