Phylogenetic Trees Based on Nucleotide or Amino Acid Sequences Can

Short Answer

Phylogenetic trees based on nucleotide or amino acid sequences can be constructed using various algorithms. One simple algorithm is based on a matrix of pairwise genetic distances (divergences) calculated after multiple alignment of the sequences. Imagine you have aligned a particular gene from different hominids (humans and the great apes), and have estimated the normalized number of nucleotide substitutions that have occurred in this gene in each pair of organisms since their divergence from their last common ancestor. You have obtained the following distance matrix.



Answer the following question(s) based on this matrix.
-The following tree can be constructed from these distances assuming a constant molecular clock, meaning that the length of each horizontal branch corresponds to evolutionary time as well as to the relative genetic distance from the common ancestor that gave rise to that branch. Indicate which one of the species in the matrix (B to D) corresponds to branches 1 to 3, respectively. Your answer would be a three-letter string composed of letters B, C, and D only, e.g. DCB.