|MadSci Network: Cell Biology|
Thanks for your question, Todd. This is an interesting question, because what you're asking is essentially what happens to create genetic diversity in offspring. What I mean is that when the sperm and egg fuse, they create a stem cell, and this stem cell has a different set of alleles than either parent.
Now, if you're asking what is possible from a scientific standpoint, to create specific kinds of genetic variation that wouldn't exist naturally, you'll probably want to know about what people have done with somatic cell nuclear transfer(SCNT). One of the world's experts in this process is Rudolph Jaenisch. The process involves removing the nucleus from an oocyte, and transplanting a somatic cell into the denucleated oocyte. The cell is then stimulated to make it think it has been fertilized, and it will begin to divide. A small number of these cells will produce viable offspring whose genetic information comes entirely from the donor of the somatic cell. It won't be identical, of course, because epigenetic modifications are made to the donor nucleus by the cytoplasm of the recipient cell, but the genes will be the same. This technique has been successfully performed in laboratory stains of mice, but no one has been able to do this with primates, though there have been some promising developments just this month, where the researchers were able to get SCNT to work. They haven't yet been successful in creating a viable organism, however.
A related technique is development of a "chimera". To do this, stem cells are genetically modified in the lab, then the modified cells are added to the blastocyst, which is the developing ball of cells resulting from the fusion of the sperm and egg that, barring problems with implantation, will develop into the embryo. The resulting offspring shares a portion of the genetic material with the donor, so in this case you can consider the stem cells to have modified the allelic makeup, even though the gametes weren't directly modified.
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