Sunday, March 27, 2011
Fossils vs. DNA
In chapter 3, Shubin talks about how he splits his laboratory into two sections: one section for fossils, and one for embryos and DNA. Shubin says that a disadvantage to working with fossils, is that you can't experiment on animals that have been long dead. What are some other advantages and disadvantages to working with fossils versus working with embryos and DNA? Danielle Webb (dwebb456@gmail.com)
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ReplyDeleteAs most would agree, the one of the advantages of working with fossils is the proof of existence to long-dead ancient animals. Fossils provide a door to the prehistoric world's organisms that modern science would not have without them. The proof gives a great advantage to scientists who study evolution to decipher our past (and perhaps provide insight to our future?) This is so, because depending on how old the fossil is (based on radioactive dating) shows what developed first, via evolution. Though fossils are unable to provide DNA evidence, the bone outlines locked in time in them still allow for the creation of fairly accurate morphological trees for classification, just not molecular trees (which are very expensive to create anyway.) Finally, a great advantage to fossils, is that their 'technology' is simple. Scientists were able to study fossils and get good information out of them long before humans were aware of DNA and genetics.
ReplyDeleteHowever, the advantages of working with embryos and DNA outnumber that of fossils. DNA provides evidence for more than just existence in a non-empirically in a way fossils simply can not provide. Additionally, embryos/DNA open up the world to experimentation with an organism that is, again, impossible for a fossil. For example, Shubin explains his lab’s work with ZPA on chickens, skates, and humans from page 55-59. This experiment would have been impossible without many embryos to work with and take data from. (Another disadvantage of fossils is that they do not provide room for error. If one accidently screws up while working with a fossil, or breaks it, they do not have another one they can re-try on. Everything must be very precise.)
However, the most ideal situation to study the evolution of our past is with the new technology that is on the rise: extracting DNA from fossils! "Fossil studies this far back in time have long been hindered by contamination with foreign genetic material and the problem of recovering long, intact DNA sequences;" however, scientists in Israel seemed to have thought of a new technique to accomplish just that (http://news.bbc.co.uk/2/hi/science/nature/4260334.stm). Hence, scientists are now able to sequence about 3/4 of the woolly mammoth genome and talk about resurrecting the ancient creature for as little as $10 million dollars. (http://www.nytimes.com/2008/11/20/science/20mammoth.html?ref=woollymammoth).
I suppose this relates to the relationship between structure and function when comparing these two methods of research. The structure of fossils preserving the shape of bones in time lends itself to the function of studying history of evolution and whatnot. DNA's structure, in that one can change it, by cutting things out or adding things in, or just the inherent amount that tends to be available for use, leads to its functions as a tool for experimentation. A fossil remains the same, a continuation of what once was. DNA sequences change throughout the course of evolution.
Jackie Edelson (jedelson92@hotmail.com)