On ...ahem... another blog, I've been having a discussion about stem cells with some folks who are convinced that unique DNA is the definition of life... in fact, PP seems to think there is no life without it. I disagree of course. Anyway, I suggested that DNA was more like the blueprint for a house, as opposed to the house itself and that there was no reason whatsoever to consider a single cell a "person." One of the opponents snapped back that my metaphor was all wet... you can build a house without a blueprint he says... well yeah but...
"You can’t build a house by throwing a bunch of nails, shingles, and lumber on the ground. There has to be organization, or in biological terms–emergent properties. A house is more than the sum of its parts, and a human being is more than a collection of DNA.
Solely using DNA to define life is weak. Are viruses alive? Or just the ones that use DNA instead of RNA? Or are no organisms that reproduce asexually alive? What about living organisms that reproduce without mixing together two genomes? What about living organisms whose dominant phase of life is the haploid (like sex cells) rather than the diploid (like body cells)?
A taxonomist would call a zygote a zygote. Perhaps a human zygote, but not a human being. To claim scientific definition of life, but to redefine what is meant by pregnancy or stages of embryological or fetal development is disingenuous. One shouldn’t pick and choose in science. Sperm cells and egg cells are just as genetically unique as a zygote. Destroying these cells destroys a potential life just as much as an embryo. The cells that give rise to sperm cells and egg cells play an active role in development.
If conception is the point where a unique human being is created, does that mean twins are not unique? When embryos fuse does that mean two unique human beings have been destroyed, despite the fact of a healthy newborn?
If removing a nucleus from an embryo equates with killing a life, does replacing the nucleus with one from a skin cell equate with saving a life? Due to accumulated mutations, this cell would also be a genetically unique individual."
Wow. Nice work, denature. Discussion?