Lab: The Molecular Connection In this activity, you will examine the amino acid sequence of Cytochrome-C proteins from twenty different species and compare that to a cladogram made using shared characters. Remember that evolution, on a genetic level, is a change in the frequency of alleles in a population over a period of time. Learning Goals: 1. Students observe the impact of different sequences of amino acids on speciation of organisms. 2. Students observe the overlap between biochemical and morphological (anatomical) similarities and differences between species. Materials: 1 data sheet of amino acid sequences in Cytochrome-C proteins from 20 different species Procedure: 1. Find the human, rhesus monkey, kangaroo, snapping turtle, bullfrog, and tuna on the data sheet provided and underline their names. You may write on the data sheet provided for the purposes of this lab. 2. Compare the human amino acid sequence with each of these five animals by counting the number of times an amino acid in that animal’s cytochrome c is different from the amino acid in that same position of the human sequence. Create a data table with two columns; organism name and the number of amino acid differences compared to human. Record the number of amino acid differences between human and the following organisms: rhesus monkey, kangaroo, snapping turtle, bullfrog, and tuna. (5 points) 3. The cladogram below shows the relationships of the selected animals based on their shared anatomical characters. For example, out of seven key traits, all of these animals have a dorsal nerve cord, but only humans, monkeys, and kangaroos have mammary glands. Make a chart (like you did with the T. Rex lab) matching the shared traits with the species that have them using + or signs. (7 points) 4. In your lab book, draw the previous cladogram and then indicate the number of amino acid differences between humans and each of the other species where the hexagons are located. (2 points) Discussion Questions (Unless otherwise specified complete sentences are required!!!): 1. Does the molecular data from the amino acid sequence differences between humans and the other organisms generally agree with the cladogram? (1 point) 2. Based on the molecular data, how does the “human-monkey” relationship compare to the “duckchicken” relationship (which shows a total of three amino acid differences when compared to each other)? (1 point) 3. If the molecular data, the structural similarities, and the fossil record all support the same pattern of relationships, can we be fairly confident that the pattern is accurate? Why or why not? (2 points – 1 answer and 1 defense) 4. Chickens and turkeys are both birds and have the same sequence of amino acids in their cytochrome-c protein. Explain how two species can have identical cytochrome-c and still be different species. (3 points – excellent, standard, weak) 5. Write a short paragraph summarizing the important information that can be obtained when viewing a cladogram. (3 points – excellent, standard, weak) Adapted from: WGBH Educational Foundation and Clear Blue Sky Productions, Inc. Copyright 2001.
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