Embryonic stem cells
Embryonic stem cells are taken from a young embryo. They may be taken from the inner part of the embryo, also known as a blastocyst, or split off at the 4 or 8 cell stage before this, leaving a viable embryo. An embryo reaches the blastocyst stage about 4-5 days after fertilization. At that point they contain about 50-150 cells.
Embryonic stem cells can differentiate into the three "germ layers": ectoderm, endoderm and mesoderm. The 220 types of cells in humans are all based on these germ layers. Some scientists have shown effectively that embryonic stem cells have greater differentiation potential, and divide into greater numbers, than adult stem cells can.
In 2001 President Bush allowed federal funding for research performed only on 60 strands of already existing stem cells. [1]. Despite the strong genetic similarities no work was done on Chimp stem cell lines.
Controversy
Pro-life conservatives consider taking stem cells from human embryos tantamount to abortion, as a potential human life is sometimes ended.
- Those who value human life from the point of conception, oppose embryonic stem cell research because the extraction of stem cells from this type of an embryo requires its destruction. In other words, it requires that a human life be killed.[2]
Many liberals, on the other hand, claim that the embryos used for stem cell research are already condemned to death because most of them are the byproduct of in vitro fertilization procedures which generate many more embryos than are needed to implant in the woman. With no further use for these embryos, they are often destroyed. Thus, liberals claim that embryonic stem cell research does not result in the destruction of any additional embryos. [3] Conservative argue that this reasoning fails to mention that embryos can be adopted within the 10 year window of viability [4] and thus saved from destruction.
