11:115:301 Lecture Notes - Lecture 5: Sequence Alignment, Myoglobin, Gene Duplication
22 Sep 2019
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Biochemical information, dna sequences, amino acid sequences, structural information about proteins, can be used to learn about evolutionary relationships between species, evolutionary relationships between proteins within a species. Paralog of human myoglobin: duplication event (hb/mb) Hundreds of millions of years ago: speciation event (human/chimp) Six million years ago: sequence alignment, align primary structure of hemoglobin and myoglobin. Compare the 2 sequences at different positions - without gaps. 2 best cases: 22 identical amino acid residues, 23 identical. Is this the best: mutations change nts and introduce deletions, insertions, rearrangements, amino acid sequence alignment with gap 38 identities, myoglobin is bigger introduce gaps. Assign score: match = 10 points, gap = -25, (38*10) - 25 = 355. Can determine the frequency with which a given aa can be functionally replaced by each of the other amino acids: blosum62 - matrix for assigning similar aa substitutions.
