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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 W2011 Lecture 3 (7 January 2011) 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 characters 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 note was uploaded on 03/09/2011 for the course BIS 2 taught by Professor Coolprof during the Spring '11 term at Bank Street College of Education.
- Spring '11