Discussion 3 Synopsis

Discussion 3 Synopsis - Discussion3synopsis...

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Discussion 3 synopsis Shamra Byrne, Jeff Jewell, Ben Garner, Huy Tran and Lisa Chen The first section of this synopsis talks about the paper by Michael Whiting discussing the reevolution of wings in stick insects and was led by Shamra Byrne and Jeff Jewell. It had previously been hypothesized that, due to its unlikely nature, stick insects could not revert from a flightless to a volant form. It was said that because current stick insects are winged, their common ancestor must have had wing function because otherwise, in order to accommodate flight, the contemporaries would have had to have developed incredibly complex interactions between multiple structures. In addition, if throughout evolution stick insects reverted from a flightless to volant form and back again, the genes for wing function, when not in use, would have accumulated so many mutations that the ability to regain wing function would be lost. However, in this article, Whiting, Bradler, and Maxwell attempt to illustrate through the construction of a stick insect molecular phylogeny and maximum parsimony that it was indeed possible that ancestral stick insects were wingless and that wings derived secondarily. They suggest that the basic framework for the wing has been conserved from ancestral stick insects and is simply re-expressed upon the recovery of wings. Because of this conservation, it is possible for stick insects to gain wings, lose them, and even gain them again through the course of evolution. Because it is difficult to classify stick insects into distinct phylogenetic groups, current classification is based mainly off of morphological traits. For instance, most stick insects are either large terrestrial or arboreal insects that exhibit extreme morphological and behavioral crypsis, meaning that they have an uncanny ability to blend in with their surroundings. In addition, they are characterized by several distinctive traits such as prothoracic repellant glands, male vomer, and the absence of mitochondria in spermatozoa. Whiting et al had a tough task ahead of them. The classification of Family Phasmotodea into phylogenetic groups was by no means a small task due to the reasons listed above. In order to try and accurately classify these insects his lab had to use genetic markers to help link groups phylogenetically. They chose to use ribosomal DNA as a genetic marker because it is found in all cells, has relatively easy access due a conserved flanking region which allows use of universal primers and has a repetitive arrangement allowing for PCR. Historically only a portion of the ribosomal DNA was used; the 18s region. However, contrary to initial high expectations, it was found that the 18s region cannot resolve nodes at all taxonomic levels therefore multi gene analysis is required in order to more accurately place nodes. So, the lab also used the 28s region of ribosomal DNA and a portion of histone 3. Once the genetic data was collected it was entered into a computer program to try and create a
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This note was uploaded on 10/24/2010 for the course BIOL 514 taught by Professor Goldstein during the Fall '10 term at UNC.

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Discussion 3 Synopsis - Discussion3synopsis...

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