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AP Biology Amino Acid Evolutionary Relationships Name_________________________________________ Homologous structures are structures that are believed to have a common origin. Similar structures or features in organisms are helpful because they can be used to trace how species migrated over time. If two species in two different locations are similar in some way it is either because both species randomly developed the same feature or the two species at one point were one species in one location. Both scenarios happen often. Thanks to modern technology, we no longer have to focus solely on physical phenotypes. DNA and amino acid sequences often tell us much more about the relationship of species than other previouslyprized features such as type of limbs or similar habitats. In this investigation you will compare amino acid sequences in proteins of several vertebrates. You will also study amino acid differences and infer evolutionary relationships among some diverse organisms. Part A: Comparing Amino Acid Sequences 1. Examine Figure 1, which compares corresponding portions of hemoglobin molecules in humans and five other vertebrate animals. Hemoglobin, a protein composed of several long chains of amino acids, is the oxygen-carrying molecule in red blood cells. The sequence shown is only a portion of a chain made up of 146 amino acids. The numbers in Figure 1 indicate the position of a particular amino acid in the chain. Figure 1 87 88 89 90 91 92 93 94 95 96 97 98 99 100 Human THR LEU SER GLU LEU HIS CYS ASP LYS LEU HIS VAL ASP PRO Chimpanzee THR LEU SER GLU LEU HIS CYS ASP LYS LEU HIS VAL ASP PRO Gorilla THR LEU SER GLU LEU HIS CYS ASP LYS LEU HIS VAL ASP PRO Rhesus GLN LEU SER GLU LEU HIS CYS ASP LYS LEU HIS VAL ASP PRO Horse ALA LEU SER GLU LEU HIS CYS ASP LYS LEU HIS VAL ASP PRO Kangaroo LYS LEU SER GLU LEU HIS CYS ASP LYS LEU HIS VAL ASP PRO 101 GLU GLU GLU GLU GLU GLU 102 Human ASN Chimpanzee ASN Gorilla ASN Rhesus ASN Horse ASN Kangaroo ASN 116 HIS HIS HIS HIS ARG GLU 103 PHE PHE PHE PHE PHE PHE 104 ARG ARG LYS LYS ARG LYS 105 LEU LEU LEU LEU LEU LEU 106 LEU LEU LEU LEU LEU LEU 107 GLY GLY GLY GLY GLY GLY 108 ASN ASN ASN ASN ASN ASN 109 VAL VAL VAL VAL VAL ILE 110 LEU LEU LEU LEU LEU ILE 111 VAL VAL VAL VAL ALA VAL 112 CYS CYS CYS CYS LEU ILE 113 LEU LEU LEU LEU VAL LEU 114 LEU LEU LEU LEU VAL LEU 115 ALA ALA ALA ALA ALA ALA 2. In Data Table 1, write the abbreviated name of each amino acid in chimpanzee hemoglobin that is DIFFERENT from that in human hemoglobin. If there are no differences, leave the spaces blank. 3. Repeat for each of the remaining four species, always comparing them to the given HUMAN hemoglobin. Complete Data Table 2 Part B: Inferring Evolutionary Relationships from Differences in Amino Acid Sequences 1. Another commonly studied protein is cytochrome c. This protein, consisting of 104 amino acids, is located in the mitochondria of cells. Its function is a respiratory enzyme (part of the electron transport chain). Figure 2 below shows the number of differences in the amino acid sequence between humans and each named species. Figure 2 Species Pairings Number of Differences Human—chimpanzee 0 Human—fruit fly 29 Human—horse 12 Human—pigeon 12 Human—rattlesnake 14 Human—red bread mold 48 Human—rhesus monkey 1 Human—screwworm fly 27 Human—snapping turtle 15 Human—tuna 21 Human—wheat 43 2. Using Figure 2, construct a bar graph to show the amino acid differences between humans and other organisms. 3. Now examine Figure 3 below. In this figure, the cytochrome c of a fruit fly is compared to the amino acid sequences of several other organisms. Construct a 2nd bar graph to show these differences. Figure 3 Species Pairings Number of Differences Fruit fly—dogfish shark 26 Fruit fly—pigeon 25 Fruit fly—screwworm fly 2 Fruit fly—silkworm moth 15 Fruit fly—tobacco moth 14 Fruit fly—wheat 47 4. Answer the following questions as a group. Use a codon chart if necessary: a. Which organisms are most/least related based on hemoglobin? Explain your answer b. Which organisms are most/least related based on cytochrome c? Explain your answer c. Which pair of organisms seem to be equally related to humans based on cytochrome c? (Hint: your answer should not include “humans.”) d. Is it possible the organisms in question “c” are both related to humans but not related to each other? Explain your answer e. There is only 1 amino acid difference between humans and gorillas. Hypothesize what could have caused this? Data Table 1 Human Chimpanzee Gorilla Rhesus Horse Kangaroo Human Chimpanzee Gorilla Rhesus Horse Kangaroo 87 THR 88 LEU 89 SER 90 GLU 91 LEU 92 HIS 93 CYS 94 ASP 95 LYS 96 LEU 97 HIS 98 VAL 99 ASP 100 PRO 101 GLU 102 ASN 103 PHE 104 ARG 105 LEU 106 LEU 107 GLY 108 ASN 109 VAL 110 LEU 111 VAL 112 CYS 113 LEU 114 LEU 115 ALA 116 HIS Data Table 2 Organisms Human and Chimpanzee Human and Gorilla Human and Rhesus Monkey Human and Horse Human and Kangaroo Number of Amino Acid Differences Positions in Which They Vary
