Copy Choice Method By Belling

Copy Choice Method By Belling

Copy Choice Method By Belling - The copy choice mechanism was first proposed by Belling (1931) for chromosomal recombination in higher animals. There are several difficulties in the copy choice mechanism (i) Copy choice accounts for the formation of only one of the two complementary recombinants. (ii) Moreover, the recombinants must necessarily contain newly synthesized DNA only, and not the DNA of the parent phages. Meselson and Weigle (1961) have shown on the basis of radioactive labelling experiments that lambda phage recombinants do contain a part of the DNA of the parents taking part in the cross.

It was proved that genetic exchange occurs by breakage and reunion, rather than by the copy choice mechanism. (iii) Recombination can occur in the absence of DNA synthesis, as shown by the experiments of Tomizawa and Anraku (1964). DNA synthesis was blocked in phage-infected cells treated with KCN, but there was no interference with recombination. This observation can only be accounted for by the break and fusion mechanisms. The copy choice mechanism is now of historical importance only

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