Discussion4Synopsis - Discussion 4 Synopsis A common plan...

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Discussion 4 Synopsis “A common plan for dorsoventral patterning in Bilateria” Katherine Reichalt, Afshin Humayun, Leslie Fincher, Devin Holland and Jimmy Fay In 1822, French naturalist E. Geoffroy Saint-Hilaire proposed there was an inversion of the dorsoventral axis during evolution. After dissection of a lobster, he observed that when turned upside down the lobster’s CNS was above the digestive tract which was above the heart. This is parallel to how the vertebrate dorsoventral pattern is constructed. The ventral region of Drosophila is homologous to the dorsal side of vertebrates. Evolutional studies regarding dorsoventral patterning and the body plan are giving rise to homologous structures characteristic to a hypothetical common ancestor, Urbilateria . Evolutionary biology follows to what extent animals have homologous structures that have been derived from a common ancestor. In order to be classified as a homologous structure, the trait must have a similar structure, pathway of development, and molecular and genetic basis. The pectoral fin of fishes, the forelimbs of vertebrates, and the wings of bats are examples of homologous structures. In comparison, analogous structures are a product of convergent evolution, and similarities in structures arose from the need to perform similar functions, such as wings in the wings of birds and flies. Drosophila and Xenopus each have a gene that allows for dorsoventral patterning. Drosophila exhibits dorsoventral patterning due to the sog (short gastrulation) gene and Xenopus exhibits dorsoventral patterning due to the chd (chordin gene). One difference between the two is that sog is initially expressed on the ventral end of the blastoderm and gastrulates on the dorsal end. The opposite is true of Xenopus where chd is initially expressed on the dorsal end of the blastopore and gastrulates on the ventral end. After studies were conducted injecting sog mRNA into Xenopus and chd mRNA into Drosophila it was shown that chd and sog behave functionally in the same manner and that they are homologues of one another. However sog mRNA in Drosophila produced a ventralizing effect and chd mRNA in Xenopus produced a dorsalizing effect. Therefore the function of the
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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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Discussion4Synopsis - Discussion 4 Synopsis A common plan...

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