1. A transgenic animal except man carrying a modified endogenous locus PIK3CA, wherein said modified endogenous locus contains an inactive PIK3CA mutant PIK3CA exon 20 encoding H1047R, adjacent to the exon 20 of the wild type, despite the fact that the above transgenic animal other than human, is capable of conditional expression of mutant alleles PIK3CA H1047R (PIK3CAe20H1047R) .2. A transgenic animal other than humans, according to Claim. 1, characterized in that the conditional expression of said mutant allele under control of the endogenous promoter PIK3CA.3. A transgenic animal other than humans, for n. 3, characterized in that said conditional expression is triggered by activation of said mutant allele by Cre mediated rekombinatsii.4. A transgenic animal other than humans, according to Claim. 1, characterized in that said conditional expression is tkanespetsifichnoy.5. A transgenic animal other than humans, for n. 4, characterized in that said conditional expression is specific for breast zhelezy.6. A transgenic animal other than humans, according to Claim. 1, characterized in that said conditional expression results in expression of the mutant and PIK3CAH1047R onkogenezu.7. A transgenic animal other than humans, in any of the claims. 1-6, characterized in that it is gryzunom.8. A transgenic animal other than humans, for n. 7, characterized in that it is a mouse or krysoy.9. Tumor bearing transgenic animal other than human, conditionally expressing a mutant allele PIK3CA H1047R (PIK3CAe20H1047R) under the control of the endogenous promoter PIK3CA.10. Tumor bearing transgenic animal other than human, according to claim. 9, wherein the mutant allele expresses PIK3CA H1047R in a tissue-specific pho1. Трансгенное животное, кроме человека, несущее модифицированный эндогенный локус PIK3CA, причем указанный модифицированный эндогенный локус PIK3CA включает неактивный мутантный PIK3CA экзон 20, кодирующий H1047R, смежный с экзоном 20 дикого типа, притом, что указанное
