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Dynamic unwinding of DNA helices: A mechanism for genetic recombination

1974; Elsevier BV; Volume: 43; Issue: 1 Linguagem: Inglês

10.1016/s0022-5193(74)80051-2

1095-8541

David Moore,

Bacterial Genetics and Biotechnology

A model of recombination is discussed in which the process is initiated by the unwinding of the DNA helix rather than by breakage of one or both of the component strands of the helix. It is argued that initial breakage is unattractive as the causal event in recombination from the evolutionary point of view and that it creates difficulties in interpretation even when considered against the background of the present day cellular environment. In contrast it is shown that initial unwinding is capable of producing a configuration which specifies precisely the positions at which breaks must occur and which is thereby able to generate recombination events in any situation in any organism. Considerable support, both theoretical and experimental, exists for the concept of helix unwinding, and particularly for the idea that DNA helices exist in solution in a dynamic state in which short regions are continually being unwound and rewound. The model of recombination developed from these arguments accounts for the generally observed features of the process at both intragenic and intergenic levels, and in addition provides explanations for more subtle phenomena like polarization, allele-specific marker effect and positive interference. The basic assumptions of the model are shown to be capable of forming the basis of explanations of inter-chromosomal effects like synapsis and the production of chromosomal aberrations. The arguments so developed, again having a firm foundation in the known biophysical characteristics of DNA, suggest an unusual reason for chromosomal organization and structure. Possible experimental tests of the concepts on which the various suggestions are based are indicated.