HOMOLOGOUS RECOMBINATIONS IN TRANSGENIC MICE WITH GENE OF NEOMYCINPHOSPHORYBOSYLTRANSFERASE Ginkul L.B., Shvemberger I.N. Institute of Cytology, Russian Academy of Sciences, St.Petersburg, Russia The concept of genome stability is commonly accepted; due to this stability, hereditability of signs is performed. However, recently, an increasing attention of many geneticists has been paid to instability of genome. This problem is very important, as it is essential to know forms and amount of such instability as well as its effect on physiological processes and, of course, on heredity. At present, point mutations are established to take place in genome more frequently than it was thought earlier. Recently it has become evident that the majority of point mutations are neutral for life because either their effect on cells is not significant or the cells-mutants are eliminated from an organism by apoptosis. A great attention is paid to the role of micro- and mini-satellites, of mobile gene elements in the genome stability, and of homologous DNA recombinations in the normal cell functioning, in development of pathology, particularly of malignant growth, and in evolution. To elucidate effects of the homologous DNA recombination on the animal organism, we used transgenic mice carrying gene of neomycinphosphoribosyltransferase (neo) with two deletions in the 3'- and 5'-sites of gene. Homologous recombination was revealed in all 8 examined transgenic mice neo. The set of tissues, in which the homologous DNA recombination of the gene neo was found, differed in mice from different parents. At the same time, the set of such tissues in F1, F2 mice — offsprings of one parent — coincided to a significant degree, which indicates heredity of such recombination. This means that either efficiency of the homologous DNA recombination of gene neo differed in different tissues or this recombination occurred at different moments of tissue differentiation. Recombination of the neo gene most likely took place at the period of embryogenesis and the subsequent growth of organs. It is to be noted that the homologous recombination neo did not affect the mice phenotype. This allows the conclusion to be made about the possible neutral character of recombination processes in genome in nature. The fact that recombinations occurred in different mice in different organs means that this process has a purely stochastic character. The recombinations able to play a role in development of pathology and in evolution.