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Humans have 46 chromosomes: 23 come from the mother (egg); 23 from the father (sperm). An egg without a sperm has only 23 chromosomes; it must be "fertilized" by the sperm to be endowed with all the genetic information (carried on the DNA of the 46 chromosomes) required for life.
All cells in the body are derived from this one fertilized egg. All the cells have the same chromosomes; the same DNA. What makes cells different is that different parts of the DNA are active in different cells. This activity is controlled by the activity of proteins and RNA (two things which are derived from the information carried by DNA).
The fertilized egg is a stem cell, but it's not the only stem cell. The fertilized egg divides into two cells and then four cells and then 8 cells. A stem cell can give rise to all of the tissues and organs necessary to make a human being. At a certain point, however, the stem cell becomes a "committed" cell. It can no longer make a human being. It can only make a certain type of tissue.
The "first generation" method of making a stem cell is to take an egg from a woman and fertilize the egg with donor sperm (actually a bunch of eggs, as excess embryos are typically created in in vitro fertilization clinics at the same time; the excess eggs/embryos are stored in liquid nitrogen for possible latter use). The fertilized egg is allowed to divide several times in cell culture, resulting in a little ball of typically 4 - 16 stem cells; in effect, the earliest embryo. This first generation technology type of stem cell is objectionable to the Catholic Church.
But stem cells will shortly be able to be created using a "second generation" technology. Take an adult skin cell; introduce a small number of genes which direct the "committed" adult skin cell to revert all the way back to an embryonic stem cell; potentially capable of not only being used for stem cell research, but potentially capable of developing into a human baby, given the proper growth conditions.
This "second generation" technology stem cell would have the same genetic material and the same capabilities as a "first generation" technology stem cell. It would be the same cell as it was at the time it was a newly fertilized egg. It would genetically be an identical twin; a clone of the original fertilized egg, in every sense of the word. This "second generation" technology is acceptable to the Catholic Church.
But the cells are the same. In one case, the cells are created by going forward (fertilizing an egg). In the other case, the cells are created by going backwards (introducing a handful of gene to reprogram the DNA of an adult cell, so that the cell reverts back to the state of a newly fertilized egg). But the cells potentially are the same, with the same potential for developing into a baby. In point of fact, it may well be that the first cloned human baby will come from this "second generation" technology and not from the "first generation" technology which everyone worries about. By officially sanctioning research into this "second generation" technology, the Catholic Church may actually be lending their support to a technology which has the greater potential for being used for a purpose they condemn (the cloning of a human).
This is a very new development. The technology was first developed/reported in Japan. It's now been independently confirmed at Harvard, currently the US leader, because they've got a lot of private money to do the work (Larry Weisenthal's older daughter has been working with it at Harvard). California labs will shortly be up and running. Initial work has been done with mouse embryonic stem cells and mouse skin cells "turned back" to embryonic stem cells.
It is hardly a remarkable event. All cells from a single individual have the same DNA. It's only a matter of controlling which part of the total DNA is active. Everything is derived from that fertilized egg. There's no reason a cell can't be reprogrammed to return to precisely the state it was in which it was a primitive embryonic stem cell or the original stem cell -- the fertilized egg itself.
In terms of them being 100% identical, save for the 4 extraneous genes introducted to turn the non-pluripotent skin (somatic) cell back into a true embryonic stem cell, these genes would either silence themselves spontaneously or could be silenced using already available technology (e.g. RNA interference).
There are a number of reasons to believe that it might actually be easier to clone a human by going backwards (2nd generation technology) than going forwards (first generation technology), which is based on introducing a somatic cell nucleus into a potentially "hostile" environment of an egg from a different person (who is not a clone of the individual from which the somatic cell nucleus was obtained).
The scientific wing of the Catholic Church has not figured this out and is basically embracing this "2nd Generation Embryonic Stem Cell Technology" as a fig leaf for withdrawing from the stem cell wars, which is a Genie which has forever escaped from the bottle.
The hypocrisy stemming from the Catholic Church is astounding. I guess God is in the test tube in the First Generation process, but no where to be found in the Second Generation process. God's will just has no bearing at all on the 2nd process.....go figure. Fear not, when the Pope figures out the mistake here, the Catholic Church will try to squash any support and make everyone's life miserable.
People of Faith muck it up for humankind when they let their senseless and inconsistant edicts stand in the way of harmless research, makes the case stronger that their rules and beliefs make little sense.
[Posted by: gpawelski at October 14, 2007 2:25 PM]
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