Posted on 10/19/2007 8:02:54 PM PDT by neverdem
Last winter, two female Komodo dragons at separate zoos in England gave their keepers big surprises. With no contact from any male, each of the giant lizards laid a clutch of viable eggs, some of which hatched healthy young (SN: 12/23/06, p. 403). The events made the news because they were the first known examples of the species reproducing by the asexual process of parthenogenesis, or virgin birth.
SELF-STARTER. A woman's eggs keep a spare set of chromosomes inside a small pouch called a polar body (arrow) until a sperm delivers the paternal set. Scientists can spur the egg to reclaim these extra chromosomes and begin growing without having been fertilized.
E. Polak de Fried, Fertility and Sterility/Elsevier
Without fertilization by sperm, the animals' eggs had begun dividing. In these surprising cases, the process continued and cute little komodo dragons emerged. Viable young can also result from parthenogenesis in various species of reptiles, plants, insects, fish, and birds.
Mammals normally can't reproduce by parthenogenesis, but that very fact is making the process interesting in a different way: It suggests a possible solution to the moral issues surrounding embryonic stem cell research. Even if an unfertilized human egg is tricked into beginning to grow, most scientists say that it will lack the capacity to produce a viable pregnancy. Yet the entity could contain stem cells with the ability to develop into nerve cells, heart cells, or any other kind of cell in the body.
Stem cells hold tremendous potential for medicine and basic biological research. But acquiring these primordial cells usually involves extracting them from an embryo that has developed into a blastocyst, a hollow sphere of about 100 cells. The extraction generally destroys the blastocyst, so opponents of embryonic stem cell research say that...
(Excerpt) Read more at sciencenews.org ...
SC Ping
ummmm... But, in the case of the lizards it did result in a viable lizard. So, if a human egg did the same, why would it not also result in a viable human? Seems to me if you get an egg to grow by tricking it or exposing it to sperm, then you do in fact have a living person.
“Most” scientists say it will be non-viable.
So it’s at best only probable that such a growing entity would be non-viable.
And this doesn’t answer the ethical concerns at all. Once an ovum begins to develop, it is a human being, and deliberately killing it is murder.
If the cell genetic template is not sufficient to create a viable whole organism, then isn’t it reasonable for any partial tissue sections grown would also fail to function correctly?
These cells, however, are far from normal because of abnormalities in a process called imprinting, which normally turns off certain genes in mammals.
and went on to say...
While natural parthenogenesis doesn't produce viable embryos in mammals, more research is needed to show whether artificially activated eggs might sometimes be viable.
Seems to me that if they get good cells, then they had to destroy a life.
Another interesting point is this ...
The main reason for using a person's own cells to make stem cells for medical therapies is to prevent the person's immune system from rejecting the implanted tissues.
How often do we hear that embryonic stem cells are going to lead to miracle cures on a whole host of ailments? I don't see how this is going to help men, since we have no way of making embryonic stem cells. For that matter, how would the use of embryonic stem cells help anyone other than the people who contributed to the DNA?
"The Catholic Church probably won't issue an official decision until scientific research establishes whether such blastocysts are impotent balls of cells or viable human embryos that happen to be defective, Pacholczyk says. 'Until we have really clear and convincing evidence whether parthenogenesis makes a true human embryo, the church is not going to step into these waters.'"
"Kevin FitzGerald, a Jesuit priest and geneticist at Georgetown University in Washington, D.C., agrees that the moral issue revolves around gaining a better understanding of what is produced when scientists cause a human egg to undergo parthenogenesis. 'Since you don't naturally get parthenogenetic offspring in mammals, if you get some sort of [spontaneous] parthenogenetic growth, then yeah, that's not an embryo,'"
I'm content to await the RC Church's decision.
Is a woman destroying a life ever month she doesn't get pregnant?
That is a silly question! The fundamental difference is an unfertilized egg is not growing. These scientist are talking about "tricking" an egg into growing.
Scientists can jolt the egg into reclaiming the DNA in the polar body. The cell may then begin to develop without being fertilized.
That they acknowledge there ARE moral concerns is an indication that they admit that abortion IS murder, some claim that it is “better” than the “alternative” (letting the child live).
Every pregnancy a planned pregnancy, every child a wanted child, and no more birth defects because the disabled will be killed before delivery.
Is there cell division during menstruation?
Abnormal imprinting is what prevents a mammalian egg activated by parthenogenesis from developing much beyond the blastocyst stage. In such an egg, both members of each pair of chromosomes would have maternal imprinting, resulting in an abnormal pattern of turned-off genes.
From what I'm reading, these cells could never become a human baby. If this is really true then I'd have *no* moral qualms about using this technology to save lives.
For the other 60 percent of the genome, corresponding pairs of chromosomes differ from each other as much as they would if they had been inherited from two parents.
This seems to imply that there is a chance that the embryo could develop.
The council [on Bioethics] stopped short of recommending the technique, saying that more evidence is needed to show that such a ball of cells can't sometimes develop like an embryo
What I failed to see in this article is a valid scientific reason why ESC is preferred , or even why we want to go down this path.
BTTT
A complete understanding of the genetics of human embryological development would be priceless. I don't know if you can get that from primates. It may enable amputees to regrow limbs like salamanders.
It sounds to me as though we have enough general knowledge to “suppose” that these embryos will not be viable. The problem, in my eyes, is that you actually have to perform the procedure to find out whether that supposition is valid. Perhaps it will be done dozens of times and suddenly, ooops, we have something viable here. After all, even in the normal course of events a fair amount of embryos aren’t viable.
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