Thursday, June 15, 2006

Unnatural Reproduction

A short article in this Tuesday's Science Times by James Corman titled "Belmont, Schmelmont. You Ought to See a Cloned Mule Run." prompted me to write my first post to this blog about cloning. (Check out the article at While the cloning debate in congress and around the dinner table is heated, and has grown to include my grandfather, and Episcopal minister, in recent years, this isn't meant to be a political tirade, so I'll just offer the facts as we know them in the hopes of elevating the current state of the debate.

Cloning is essentially making a copy of something else, but when it comes to the world of biology, there just isn't a Xerox machine up to this task. The cloning we're mostly talking about is reproductive cloning, or the type that produced Dolly the sheep in 1996. There are piles of information on this process available at several different levels out there, but the main idea is that the nucleus (read "brain" or "control center") of an egg from a donor animal is removed and replaced with the nucleus of the animal to be cloned. Add a little electric current and the egg's fate is now controlled by the new nucleus. The egg, operated on outside the mother, is reimplanted and the cloned animal is allowed to develop in the normal way. This method is extremely unsuccessful and requires many replicates to produce one success. This is the method Corman was talking about in his article about Idaho Gem, the first-ever cloned mule c. 2003. This method is fairly uncontroversial, if cloning humans isn't brought up, and it's not the way in which human cells would be cloned anyway if they are to be used for medical applications. The other caveat to mention regarding this cloning method is that no clone is exactly like the animal it is cloned from. This has to do with the way in which animals grow and develop. Yes, much of the instruction for how your body will develop is controlled by your genes, but a massive, and not entirely illuminated part of your development comes from your environment and how it interacts with your genes. This is the subject of many a recent scientific journal article and the jury's still out on the matter. What it means for clones though, is that because the experience of the cloned animal, from the time it's in the womb to the time it reaches maturity, differs from the animal it's a clone of, it's genes and environment will interact differently to produce a different end product. There's no way, in other words, to make an identical copy of any animal, and that goes for identical twins as well.

The second kind of cloning is DNA cloning, which involves inserting a strand of DNA into a host, usually a plasmid in a single-celled organism, so that the host replicates and uses that DNA. This is mainly used for the study of DNA function and won't be further discussed here.

The third, and perhaps most surprising form of cloning is that which involves stem cells, another of the hotly contentious issues in the media for the past decade or so. This process involves removing the nucleus from human egg cells and replacing it with the genetic information of another cell (a skin cell for example) which causes the beginning of an embryo to form. This embryo is aborted and stem cells are harvested for research purposes. This is probably more ethical than harvesting stem cells from embryos made in the good old-fashioned way or from those from abortion clinics. Stem cells are important because they are totipotent, or have the potential to become any of the multitude of cell types in a living human. They can be stored and replicated, from stem cells ( but each of the cells in each line is more or less the same. If one in a billion stem cells shows a characteristic of interest, say a resistance to the changes associated with common diseases, it is a very small percentage of the stem cells available, and very little significant research may be performed on that cell line. With the limited number of lines available to stem cell researchers, the chances of hitting on something really important and fruitful (as so much of science research is chance) are very low.

Beyond growing you a new liver at sixty-five, which would still involved the extremely crude process of transplantation, stem cell research offers the potential to learn how to control and manage our cells, and perhaps create new therapies for diseases that operate at the level of DNA which could essentially teach our bodies to repair otherwise irreparably damaged tissues, as with Alzheimer's patients. If you're looking for the fountain of youth, this may be it, but as with so many other scientific pursuits, it's still a long way off.


At 6:36 PM, June 19, 2006, Anonymous Jim Willis said...

Blogging about the scientific method is a brilliant idea. Best of luck! I'll be sure to check back.

At 10:10 AM, December 29, 2006, Anonymous Anonymous said...

Nice site man! Very nicely done. I will be back!
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