Question

Could someone explain how to build a parsimonious tree? and which one has the maximum parsimony? (for the first question) i have a class example attached as well to show what it should look like but I dont undertand how to get the answer

Problem: build the most parsimonious tree Species Site Site Site Site с т А Т CTT C A G A C E00E Ancestral Sequence тит 2. Draw out the 3 possible trees One site at a time, mark on each tree where a change would have occurred from the ancestral state Count up all the changes. The tree with the least changes is the has maximum parsimony.

Answer 1

Species A deviates from ancestral sequence in site 1, 2 & 3. Species B deviates from ancestral sequence in site 1, 2 & 4. Species C deviates from ancestral sequence in site 3 & 4. Below three possible ways by which a phylogenetic tree can be drawn is shown.

Ancestral Sequence Ancestral Sequence Ancestral Sequence An + + + + + + + 'T A B Tree 1 (6 changes) Tree 2 (7 changes) Tree 3 (7 changes)

In tree 1, species C can be deviate from A & B at first by changing at sites 3 & 4. After changing at sites 1 & 2, species A & B deviate from each other by incorporating changes at sites 3 & 4 respectively. In this way, there are total 6 changes (Shown by blue lines) can occur over time from ancestral sequence.

In tree 2, species B can be deviate from A & C at first by changing at sites 1, 2 & 4. After changing at site 3, species A & C deviate from each other by incorporating changes at sites 1, 2 (For A) & 4 (For C). In this way, there are total 7 changes (Shown by blue lines) can occur over time from ancestral sequence.

In tree 3, species A can be deviate from B & C at first by changing at sites 1, 2 & 3. After changing at site 4, species B & C deviate from each other by incorporating changes at sites 1, 2 (For B) & 3 (For C). In this way, there are total 7 changes (Shown by blue lines) can occur over time from ancestral sequence.

As tree 1 has least changes (6) than tree 2 & 3 which both have 7 changes, tree 1 is most parsimonious tree.