1. A method for conditionally knockout allele in a cell comprising the target gene, comprising the steps of: a. introduced into the donor cell construct comprising a 5-terminal homology region, the 5-terminal site recombinase recognition donor sequence, the 3-terminal recombinase recognition site and the 3-terminal region of homology with the donor sequence comprises a target sequence having at at least one neutral mutation and b. sequence introduced into the cell-specific nuclease which cleaves a sequence within the target gene, thereby forming conditional knockout allele in kletke.2. A method according to Claim. 1, characterized in that the sequence-specific nuclease is a nuclease "zinc fingers" (ZFN) .3. A method according to Claim. 1, characterized in that the sequence-specific nuclease is a transcriptional activator such effector nuclease (TALEN) .4. The method of claim. 1, characterized in that the sequence-specific nuclease is a dimer ZFN, which cleaves the target gene only one raz.5. The method of claim. 1, characterized in that the sequence-specific nuclease is a RNA-guided nukleazu.6. The method of claim. 5, characterized in that the RNA-directed nuclease represents Cas9.7. The method of claim. 1, characterized in that the sequence-specific nuclease is introduced as a protein or mRNA kDNK.8. The method of claim. 1, characterized in that the recombinase recognition site is a site of loxP, frt site or site rox.9. The method of claim. 1, characterized in that the donor sequence contains seven silent mutatsiy.10. The method of claim. 1, characterized in that homology sequences IU1. Способ получения условно нокаутного аллеля в клетке, содержащей ген-мишень, включающий стадии, на которых:a. вводят в клетку донорный конструкт, содержащий 5′-концевую область гомологии, 5′-концевой сайт распознавания рекомбиназы, донорную последовательность, 3′-концевой сайт распознавания рекомбиназы и 3′-концевую область гомологии, причем донорная последовательность содержит после
