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Molecular Homologies All living things have DNA. The more closely related two species are, the more similar their DNA sequences are. Molecular Homologies Some proteins are common to many species. Organis Partial Amino Acid Sequence for m Cytochrome C Horse Gly-Leu-Phe-Gly-Arg-Lys-Thu-GlyGlu-Ala-Pro Kangar oo Gly-Ile-Phe-Gly-Arg-Lys-Thu-Gly-GluAla-Pro Human Gly-Leu-Phe-Gly-Arg-Lys-Thr-GlyGlu-Ala-Pro Chicken Gly-Leu-Phe-Gly-Arg-Lys-Thr-GlyGlu-Ala-Glu Tuna Gly-Leu-Phe-Gly-Arg-Lys-Thr-GlyGlu-Ala-Gly WhatGly-Phe-Gly-Arg-His-Thr-Gly-Glu-Alasimilarities do you see? Moth Pro-Gly Yeast Gly-Ile-Phe-Gly-Arg-His-Ser-Gly-Glu- If 2 species are closely related, the DNA sequences that code for a common protein should be very similar. If they are only distantly related, there should be more differences in the DNA sequence. Molecular Homologies % Difference of a Protein (Cytochrome C) Between Different Organisms Eel (Lamprey) Carp (fish) Organis m % Difference Organis m % Difference Horse 15 Horse 13 Pigeon 18 Pigeon 14 Turtle 18 Turtle 13 Carp 12 Lamprey 12 Organis m % Difference Organism % Difference Horse 11 Pigeon 11 Carp 14 Turtle 11 Turtle 8 Carp 13 Lamprey 18 Lamprey 15 Pigeon (bird) Horse (mammal) Who is the eel most like? Carp Who is the turtle most like? Pigeon Molecular Homologies Cyt-C Compared to Humans Organism Cyt C % Diff Rhesus Monkey 1 Rabbit 9 Horse Who is least like a human based on the differences in DNA? A bacterium Cyt-C Compared to a Bacterium Organism Cyt C % Diff Horse 64 12 Pigeon 64 Tuna 20 Tuna 65 Worm 25 65 Wheat 38 Silkworm Moth Yeast 41 Wheat 66 Bacterium 65 Yeast 69 What should a bacterium be most similar to? Yeast Does the data show this? Not on this table One explanation for this may be that bacteria are believed to be one of the earliest forms of life so everything else is very removed from it Developmental Homologies dogfish lamprey gar salmon lungfish hellbender Cat bat snake early Intermediate late • All vertebrates develop a similar body plan and look similar during early development. • Evolutionary scientists believe this similar development indicates a common ancestor for all vertebrates. human
