Diversity point mutations

K12. Kanno, H Wei, D. C, C Chan, L. C., Mizoguchi, H., Ando, M., Nakahata, T Narisawa, K., Fujii, H., and Miwa, S., Hereditary hemolytic anemia caused by diverse point mutations of pyruvate kinase gene found in Japan and Hong Kong. Blood 84,3505-3509 (1994). 

V14. Vulliamy, T. J D Urso, M., Battistuzzi, G Estrada, M., Foulkes, N. S., Martini, G., Calabro, V., Poggi, V., Giordano, R., Town, M., Luzzatto, L., and Persico, M. G Diverse point mutations in the human glucose-6-phosphate dehydrogenase gene cause enzyme deficiency and mild or severe hemolytic anemia. Proc. Natl. Acad. Sci. U.S.A. 85, 5171-5175 (1988). 

Vatsis KP, Martell KJ, Weber WW. Diverse point mutations in the human gene for polymorphic N-acetyltransferase. Proc Natl Acad Sci USA 1991 88 6333-7. 

All these techniques create genetic diversity by recombination and point mutations and are well developed. However, insertions and deletions (indels) are also important types of mutation which are probably underrepresented in many conventional mutagenesis strategies. Methods for incorporation of indels in predefined positions in a combinatorial manner have been developed.Although there are some published studies on their use in the directed evolution of biocatalysts,the full potential of these newer methods of gene mutation for enzyme improvement are yet to be demonstrated. 

In DNA shuffling starting from a single gene as the parent template, diversity originates from random point mutations, due to the limited fidelity of polymerases... 

A library of parent DNA sequences encoding for the desired protein is chosen. Sequence diversity is created or increased through a mutagenesis step, either by introduction of random point mutations through error-prone PCR or by recombination of DNA fragments such as DNA shuffling or RACHITT. 

Sequence alterations in viruses are common. Areas of high sequence variation may be interspersed between conserved domains. Higher frequencies of variation can be correlated with lower polymerase fidelity and may allow escape from antibody recognition and from antiviral drugs. Common mutations in viruses include point mutations, insertions, and deletions. Sequence diversity within a viral species may be so great that consensus sequences for molecular typing are difficult to find. 

CDR3 regions is readily explained by the assortment of gene segments and by junctional diversification, the genetic basis of CDR1 and CDR2 diversity appears to be the product of evolutionary processes and somatic point mutations. 

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