1 +1 = 2, not 1

Ignoring the real breakthrough concerning embryonic stem cells from adult cells, the media is all over the announcement (of old news, at that)that embryonic stem cells can be derived from cells removed from embryos. In fact, all of those embryos used in the experiment were destroyed.

The ethics questions are, (1) were 16 embryos or 16 embryos plus many of their twins destroyed and (2) if the original embryos had not been purposefully destroyed as in this experiment, would they have been harmed?

Pre-Implantation Genetic Diagnosis (PGD) is a near-routine procedure for those in vitro fertilization procedures where parents do not want to have children with certain diseases or wish to choose the characteristics of the children they do have. We know that there doesn't seem to be an effect on the implantation and gestation of those children who are chosen. There are concerns about weight gain and birth defects and objections about the ethics of experimenting on children - and their children into the future - without their consent.

So the question is whether or not the blastomeres from the 8 to 10 cell embryo are in fact single cell embryos or twins of the original embryo, themselves. I'm still not convinced, but will watch with interest further research (preferably on animals).

According to the letter (a semi-peer reviewed method of reporting research - it doesn't take as long as the usual submission process, usually is not as thorough, and not subjected to the same review and critique) in Nature, August 24, 2006 (subscription only)

Concerns have been raised as to whether individual eight-cell-stage blastomeres, such as those used in the current study, are totipotent and could potentially generate a human being. A recent report shows the localization of cell fate determinants (Cdx2) in the late-dividing blastomeres of the two-cell-stage mouse embryo17. Other studies show that at the four-cell stage, blastomeres have different developmental properties18, and that individual human blastomeres have differential Oct-4 expression that seems to direct cells towards inner cell mass or trophoectoderm lineages19. Notably, individual morula (8–16-cell)-stage blastomeres have never been shown to have the intrinsic capacity to generate a complete organism in any mammalian species.