The tasks and puzzles of cloning

The attention of researchers is drawn to the fact that, in spite of great effort put into mammalian cloning, advances in this area are quite limited, and cloned animals have developmental pathologies often incompatible with life and/or reproduction. It is not clear yet whether these shortcomings are underlain by biological or technical factors, or more likely both. There is a great number of papers dealing with the influence of cloning by nuclear transfer on genetic and epigenetic reprogramming of donor cells. At the same time, we see practically no analytical studies on the cloning procedure itself, its weak points, and possible sources of cell trauma during microsurgery of nuclear transfer or twinning. This article discusses, step by step, some nuclear transfer techniques and methods of splitting early preimplantation embryos for twinning, with the aim to reveal possible causes of cell injury in micromanipulation that would adversely affect the development of cloned organisms. Several new author’s technologies based on the study of cell biophysical characteristics are described, which allow avoiding or at least minimizing cell trauma.