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. Organism Partial Amino Acid Sequence for Cytochrome C Horse Gly-Leu-Phe-Gly-Arg-Lys-Thu-Gly-Glu-Ala-Pro Kangaroo Gly-Ile-Phe-Gly-Arg-Lys-Thu-Gly-Glu-Ala-Pro Human Gly-Leu-Phe-Gly-Arg-Lys-Thr-Gly-Glu-Ala-Pro Chicken Gly-Leu-Phe-Gly-Arg-Lys-Thr-Gly-Glu-Ala-Glu Tuna Gly-Leu-Phe-Gly-Arg-Lys-Thr-Gly-Glu-Ala-Gly Moth Gly-Phe-Gly-Arg-His-Thr-Gly-Glu-Ala-Pro-Gly Yeast Gly-Ile-Phe-Gly-Arg-His-Ser-Gly-Glu-Ala-Pro 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. What similarities do you see?

% Difference of a Protein (Cytochrome C) Between Different Organisms Molecular Homologies % Difference of a Protein (Cytochrome C) Between Different Organisms Who is the eel most like? Carp Who is the turtle most like? Pigeon Eel (Lamprey) Organism % Difference Horse 15 Pigeon 18 Turtle Carp 12 Carp (fish) Organism % Difference Horse 13 Pigeon 14 Turtle Lamprey 12 Pigeon (bird) Organism % Difference Horse 11 Carp 14 Turtle 8 Lamprey 18 Horse (mammal) Organism % Difference Pigeon 11 Turtle Carp 13 Lamprey 15

Molecular Homologies Cyt-C Compared to Humans Who is least like a human based on the differences in DNA? A bacterium What should a bacterium be most similar to? Yeast Cyt-C Compared to Humans Organism Cyt C % Diff Rhesus Monkey 1 Rabbit 9 Horse 12 Tuna 20 Worm 25 Wheat 38 Yeast 41 Bacterium 65 Cyt-C Compared to a Bacterium Organism Cyt C % Diff Horse 64 Pigeon Tuna 65 Silkworm Moth Wheat 66 Yeast 69 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 Cat bat dogfish salmon hellbender chicken possum human lamprey gar lungfish snake early Inter-mediate 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.