MOLECULAR SYSTEMATICS - sequence divergence there has been...

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MOLECULAR SYSTEMATICS Molecular biology has revolutionized the field of systematics. DNA evolves by mutations being incorporated in the DNA and fixed in populations. This will lead to divergence of DNA sequences in different species. Although diverged, we can refer to two DNA sequences as homologous (just as we would for any morphological trait such as forelimbs). Nicely demonstrates descent with modification as a definition of evolution. For this reason, DNA should be an excellent tool for inferring phylogenies: large number of homologous characters that should be (??) less subject to convergent evolution than other characters that might lead to a confusion of grade and clade. To estimate phylogenies we first must estimate how much
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Unformatted text preview: sequence divergence there has been between the various taxa we want to study. Several methods: direct sequencing . Elegant molecular methods available, a lot of work but provides lots of data. Each nucleotide position is a character and the actual nucleotide that is present at that site is the character state . A character can be phylogenetically informative when nucleotide changes are shared by two or more taxa. A character can be phylogenetically uninformative when all nucleotides are the same among taxa, or when only a single taxon has a different nucleotide. I U I A C T C G A C T A G A T A C T C G T C T A G A T A C A C G T C T A G A T A C A C G T C T A C A T A C A C G T C T A C A T...
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