In chapter 4, Shenk discusses
further about Ted Williams, the extraordinary baseball player with uncanny
skill and determination. Williams’ son, John Henry, realized the value in his
father’s genes and remarked, “What if we could sell dad’s DNA and there could
be little Ted Williamses all over the world?” (73). In other words, his intent
was to clone his father. But, as determined by Shenk, it is simply impossible
to bring him back to life “quirk for quirk and swing for swing” (73).
With this new model of GxE, exactly
how close can we get to creating a near “carbon-copy” of a human, or any
organism for that matter (if at all)? What types of environmental conditions would have to
be present in order to create this replica? Why would some organisms seem to be
easier to clone than others? How is cloning related to the various modes of
reproduction found in nature? And what are the evolutionary benefits of having
a carbon-copy of oneself, versus a genetically different one?
-Diane Kuai
(dianekuai@gmail.com)
Scientists have already cloned many organisms that have identical DNA, but environmental factors can always make these organisms appear different, even if their genomes are the same. This ties in with the GxE model, where genes do not rigidly define the phenotype of an organism; instead, they interact with the environment to produce a unique individual. Though we can make sure that the genome of the animal is identical, we can never completely control all the environmental factors that affect development, because there is simply too many unknown variables to control.
ReplyDeleteTo attempt to create a replica, we could ensure that the clones grow up with the same food, amount of exercise, and location, but we cannot prevent other factors we do not know about, that could affect the clone even before birth, such as conditions for the developing embryo. In 2002, scientists in Texas succeeded in cloning a cat. The kitten, however, was completely different from the mother, even though they were genetically identical. Their coat colors and even their temperaments were completely different-the DNA donor had a calico coat and was reserved, but the clone was playful and had a grey coat. This was because "the pattern on cats' coats is only partly genetically determined-it also depends on other factors during development" (Braun). This shows that identical genes do not ensure a "carbon-copy", which makes cloning animals, let alone humans, a task that will never be perfect.
Some organisms, however, do clone themselves-Campbell defines asexual reproduction as "a single individual is the sole parent and passes copies of all its genes to its offspring", and the offspring are called "clones" (249). Bacteria perform asexual reproduction by binary fission, and the hydra reproduces by budding. In each case, the methods of asexual reproduction are done in relatively simple animals, where there is a smaller level of body complexity. This makes cloning easier because the organism's primitive genes will not have as much of a complex interaction with its environment, as opposed to a human or cat. Asexual reproduction holds benefits for these types of organisms because, if the organism already has favorable genes, it would help the offspring to recieve those genes intact. Also, it eliminates the struggle of finding a mate. Making a carbon-copy of themselves has served many simple organisms well, but for more complex animals, having sexual reproduction for variation works better.
(http://news.nationalgeographic.com/news/2002/02/0214_021402copycat.html)
-Akila Khan (starlight608@gmail.com)