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Unformatted text preview: least amount of change in character states (i.e., the fewest “steps” where a step is a change from one character state to another) BIS2C W2012 Lecture 3 (11 January 2012) Unrooted tree: a tree in which the root has been removed An unrooted tree shows branch splitting events but not the temporal sequence of these events. Basic procedure for finding/searching for the most parsimonious tree: 1. Ignore parsimony-uninformative characters. 2. Draw possible trees. 3. For each informative character count the minimum number of steps required on each tree. 4. Sum over all character s to get the “score” (number of steps) for each tree. 5. The most parsimonious tree(s) is/are the one(s) with lowest score. 6. Root the tree along the branch leading to the outgroup (if known). Example: four-taxon problem. Characters 1 2 3 4 5 6 7 8 9 Taxa M antid C T G G A C C C T W asp C T A G C T C C C B eetle C T G G C C A C T F ly T T A G C T A C T...
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This document was uploaded on 03/12/2012.
- Spring '08