Turning on Genes
Date: Winter 2012-2913
Hi, I read about geneticists ability's to "turn on" genes, they said it was possible to turn on certain genes that had been dormant within an animals DNA lets say a dolphin so my question is could you turn on the gene that makes a dolphin grow legs?
Thanks for the question. In principle, it may be possible to "turn on" a gene and then the a dolphin may be able to grow legs. However, the gene in question has to be present in the genome. For example, you can't turn on the gene for fingernails in a dolphin because that gene is not present in the genome of the dolphin. In principle, it does not matter whether the gene is dominant or recessive.
I hope this helps. Please let me know if you have any more questions.
Search for "atavisms dolphin" and you will find a picture of a dolphin with rear fins, but not legs. An atavism is a trait that seems to be a throwback to an earlier evolutionary state. Another example would be a "tail" in humans. This would actually just be extra coccygeal vertebrae. It does seem that during embryological development traits can be turned on or not and would have a significant effect on the morphology (body) of the organism.
That is certainly an interesting question! The short answer to your question is that dolphins already have structures that are homologous to legs, so in a sense they already grow legs.
Nevertheless, the underlying question is an interesting one - could we use clever genetic engineering techniques to make a hybrid organism that has traits from several different unmodified organisms? The simple answer is that scientists routinely do precisely this. For example, food crops (such as corn or rice) are often engineered to make them more resistant to drought or pesticides, or to make them thrive in saltwater, or any number of other uses. This is normally done by finding a useful gene in another organism and inserting it into the plant's genetic code. Even before modern genetic engineering, livestock and crops were routinely bred and hybridized to make new organisms.
The more complex answer is that it's possible - with a lot of trial and error - to add a trait to an organism, but it can be very difficult to add more and more complex structures and functions. If we wanted corn to grow on a tree, for example, that would probably be beyond our current technology given the sheer complexity involved in doing so (it also might not make much sense economically). Going back to your example about a dolphin, it is at least conceivable that a highly sophisticated research project could take a dolphin embryo and change its genetics enough to give it legs that looked and functioned roughly like a land mammal's. The amount of work involved, though, would be so significant as to make it essentially impossible using current technology. I find it questionable, though, that one would be able to do this without changing the dolphin's genetics so much as to make it essentially unrecognizable as a dolphin.
S. Unterman Ph.D.
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Update: November 2011