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Cloning Yields Human-Rabbit Hybrid Embryo
ralphb writes "Here is the story of scientists in China who have, for the first time, used cloning techniques to create hybrid embryos that contain a mix of DNA from both humans and rabbits. Hop on over for a look!"
if the US wasn't strictly trying to control embryonic stem cells for research, then there wouldn't be a demand to make a hybrid source for embryonic stem cells.
america (currently) leads because we (usually) have the foresight to keep barriers out of the way of technological progress. we have slowly overcome nearly every 'religious' boundary by slowly letting people become accustomed to the way this medical technology -improves- life. each time they are accused of wanting to 'play god'. scientists grit and bear the well-intentioned but factually ignorant viewpoint until slowly the advances are accepted.
i'm not saying that we throw our morals to the wind and race to immortality and superhuman hybrids - just that we redirect our skepticism. are we really trying to play god? or are we just trying to preserve and extend life, to ease pain and suffering, and to advance as much of our species as we can, without hurting anyone? instead of just levelling opposition to every potential breakthrough because we're 'playing god' - can't we just look for a second at what the facts are?
embryonic stem cells are being harvested from aborted fetuses. fetuses that were legally terminated and currently, are waste. by banning science from using this unfortunate situation to the best of their ability, people are ensuring that absolutely no good comes from the situation.
if lives can be saved by studying those who have left - then why in the world would we stand in the way of that? religious opposition in the 19th and early 20th century maintained that if we allowed study of cadavers or donation of organs that people would be killed and abducted and harvested by notorious individuals in the name of 'science'. but that did not happen. nor will people go out of their way to abort fetuses just so they can get stem cells. scientists are not growing fetuses to harvest stem cells.
this unfortunately ignites the whole abortion debate, which i doubt will ever be resolved. but legally, if I, as next of kin, have the right to determine whether the body of a loved one is to be donated to science; why shouldn't these mothers who exercised their legal right to terminate their pregnancies, also have that same legal right to donate?
// "Can't clowns and pirates just -try- to get along?"
First off, they had to remove virtually all the rabbit nuclear DNA because if you do not do this and simply fuse two cells (say a human cell and a rabbit cell) with intact DNA, almost invariably, the human DNA is lost. The cells dump extraneous DNA and it just happens that most often, it is the human chromosomes that get dumped.
Second, this is merely a gradation of "chimera" beyond that which is commonly called a "transgenic". The later is a long-used basic tool in molecular biology/developmental research. There are innumerable extant mouse-human "chimeras" out there, just as there are Drosophila-human, yeast-human, yeast-E. coli, E. coli-yeast, etc, etc, etc, transgenic (chimeras). Normally, what is transfered in these cases are individual genes, though short chromosomal segments can be transfered as well. This article refers to a chimera in which it is merely the shell that contains the DNA (the cell) that is changed from native to alien species. You could likely get by with a viable cell with a partial mix of rabbit genes in human cells and vice versa, so long as the proteins encoded by the genes are homologous enough to share the same functions and helper proteins.
What would be cool, in my opinion, would be to do a human-bird hybrid in which the bird cell contains only human genomic DNA but the cells retain avian mitochondria - with a little transgenic work done to replace the human mitochondrial genes in the nuclear chromosomes with their avian counterpart. Why? IF (a relatively big if) the mitochondria can properly function in concert with the rest of the human DNA, you might produce a long-lived cell line or, if you let it go to term, a longer lived human. Why? This is based on the oxidative damage/free radical theory of aging: bird mitochondria are much more efficient than human mitochondria on the level of producing energy (ATP) vs production of damaging oxygen radicals. Birds have a high metabolism and their lifespan, relative to metabolic rate (one of the supporting observations for the free radical theory of aging), is unusually long. In general, a higher metabolic rate equates to a correspondingly shorter lifespan. The predominant source of damaging radicals is mitochondria by far. So, if you replace the human mitochondria with super-efficient, low radical producing bird mitochondria, you could end up with a human with an extended lifespan (to unknown extent) if the free radical theory of aging is largely correct.
Such a person would be no less human than anyone else, their mitochondria would simply be that of a bird rather than a human. Big deal. Mitochondria are alien themselves, afterall. They are the remnant of the fusion, hundreds of millions of years ago, between an anaerobic-type cell and a cyanobacteria-like aerobic bacteria. Once upon a time, then, a chimera was formed based on a semi-parasitic melding of two separate species. Each gains benefit from the other and ultimately, you end up with aerobic eukaryotic cells that makes humans, dogs, birds, insects, reptiles, etc.
In Bushworld, they struggle to keep church and state separate in Iraq as they increasingly merge the two in America.
These probably would not survive gestation. There are factors spread out in a specific manner in an egg which tell the various parts of the embryo what to become, and when. Imagine the egg as a bag of concentration gradients, going along at least three axes, several gradients per axis. As the cell divides, these become compartmentalized into individual cells. You now have scores of little bags with codes to each one, the code being the concentration of several factors (factors ABCDE having respective concentrations of 4,3,1,2,6 or 5,4,0,8,9). At certain times, these factors come together and give signals that tell that cell or group of cells to become a certain progenitor tissue type. Differentiation goes further after that, with cells "deciding" what to become based on what kind of cell is nearby.
Many of the signals would be similar between human and rabbit, but probably not enough to make a viable human, or viable anything else for that matter. The rabbit DNA control sequences targeted by the factors that are in the egg would probably be too different from the sequences with similar function in human DNA. This would permit the embryos to survive through several divisions, and probably form simple embryos (mammals are very similar until the fetus stage....even then, it's hard to tell sometimes). But it would probably never make it through gestation. Probably.
There is a reason for everything. Sometimes that reason just sucks.
Small nitpick. You're referring to trisomy, not triploidy. Trisomy (in humans) refers to an inadvertant tripling of one chromosome; triploidy is the result of an extra (third) copy of all chromosomes. Triploidy is usually the result of two sperm fertilizing a single egg. (Oops.) Trisomy (or monosomy, where the fetus is one chromosome short) is usually the result of an uneven division of genetic material when sperm or egg was formed.
Triploid fetuses usually spontaneously abort, though some will survive to term--in which case their life expectancy is less than a month.
As you noted, some trisomies are survivable; most are not. More details here.
Interesting aside: Some species (particularly plants) tolerate polyploidy quite well, having tetraploid or hexaploid genomes (four or six sets of chromosomes). Odd numbers of sets are infertile, but again are often tolerated in plants--this infertility is sometimes a desired trait, as in seedless watermelons and grapes.
~Idarubicin