Embryo stem cells : biological data

Biology teaches us that the fusion of the parents’ gametes (the ovocyte and spermatozoid) at the moment of fertilization generates a new entity that is distinct from these 2 gametes, with a genetic code so unique that it has never existed before in other living beings and will never exist again. This genetic code is found in the very first cell and will be found in each of the billions of other cells produced. From the first cell onwards, biological analyses show that we are in the presence of a human being rather than a being from another species.

Once, each of us consisted of a single cell. Whilst growing, each of us acquired skills, and each of us will see our strength decline. But, regardless of the development stage, we are of course still talking about the same human being, who has the same dignity. Between the stage involving the first cell of the embryo (called the “zygote”) and that of an old man, along with the intermediate stages of the embryo (the “morula”, and “blastocyst”), and the stages of infancy, there is no genetic break; no basic modification of the being in question occurs. The only difference is a temporal one.

Up until the stage of the 8th cell (on the 4th day approximately), the embryo’s cells are totipotent; in other words, taken in isolation, they are capable of constituting a full organism. Above and beyond that, they become pluripotent: they can form all of the organism’s tissues but not a whole individual. It is at this 5th day stage that the embryo is punctured by certain laboratories, following which it is dislocated, placed in a synthetic culture medium, and is therefore actually destroyed. The embryos used are sampled from a stock of frozen embryos constituted during in vitro fertilizations. In France in 2011, approximately 165,000 embryos were frozen, including 34 % for which there was no so-called “parental project”.