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Embed code for: Amino acid sequencing lab
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Guided Inquiry • Skills Lab
Chapter 16 Lab Amino Acid Sequences: Indicators of Evolution
1. Predict Based only on their anatomy, rank gorillas, bears, chimpanzees, and mice from most recent common ancestor with humans to least recent common ancestor.
2. Use Analogies You tell a story to a second person who tells it to a third person, and so on. As the story is retold, changes are introduced. Over time, the number of changes increases. How is this process an analogy for what happens to DNA over time?
3. Infer Hemoglobin from two species is compared. On the long protein chains, there are three locations where the amino acids are different. Where would you place the common ancestor of the two species on the “tree of life,” (late or recent) and why?
Part A: Comparing Amino Acid Sequences in Hemoglobin
Hemoglobin is the molecule in blood that carries oxygen. This complex molecule contains four protein chains. Figure 1 shows the amino acid sequence for one of those chains in eight mammals. Each letter stands for a different amino acid. Each column is a location on the protein chain. note: Locations where the amino acids are identical in all eight mammals are not shown.
1. Use the row labeled Human as your control. Compare the sequence for the bear to the sequence for humans. When you find a difference in the bear sequence, highlight it.
2. Repeat Step 1 for each of the other mammals. Be sure to compare each sequence to the sequence for humans.
Figure 1 Comparison of amino acid sequences in hemoglobin from eight mammals
4 5 6 9 10 12 13 20 25 33 41 43 50 51 52 Human T P E S A T A V G V F E T P D Bear T G E S L T G V G V F D S A D Chimpanzee T P E S A T A V G V F E T P D Gibbon T P E S A T A V G V F E T P D Gorilla T P E S A T A V G V F E T P D Monkey T P E N A T T V G L F E S P D Mouse T D A A A S C S G V Y D S A S Shrew S G E A C T G E A V F D S A S
54 56 58 68 69 70 71 72 73 75 76 77 80 87 104 Human V G P L G A F S D L A H N T R Bear I N P L N S F S D L K N N K K Chimpanzee V G P L G A F S D L A H N T R Gibbon V G P L G A F S D L A H N Q R Gorilla V G P L G A F S D L A H N T K Monkey V G P L G A F S D L N H N Q K Mouse I G A I T A F N D L N H S S R Shrew V G P L H S L G E V A N N K R
109 110 112 115 116 117 118 121 125 126 130 139 Human V L C A H H F E P V Y N Bear V L C A H H F E Q V Y N Chimpanzee V L C A H H F E P V Y N Gibbon V L C A H H F E Q V Y N Gorilla V L C A H H F E P V Y N Monkey V L C A H H F E Q V Y N Mouse M I I G H H L D A A F T Shrew V L V A S K F E P V F N
3. In the space below, make a data table (look to #4 below for an example) to record the number of differences you found for each mammal in comparison to humans.
Part B: Differences in Cytochrome c
Cytochrome c takes part in electron transport during the last stage of cellular respiration. This enzyme can be found in bacteria, yeasts, fungi, plants, and animals. The human cytochrome c molecule is relatively small. Its single strand of protein has 104 amino acids.
4. In Figure 2, human cytochrome c is the standard. Column 1 lists the species that are being compared to humans. Column 2 lists the number of differences for each pairing. Use the data to make a bar graph on a separate sheet of graph paper. Rearrange the order of species to go from least to most.
Figure 2 How human cytochrome c differs from cytochrome c found in other species
Species Number of Differences Chimpanzee 0 Fruit fly 29 Horse 12 Pigeon 12 Rattlesnake 14 Red bread mold 48 Rhesus monkey 1 Snapping turtle 15 Tuna 21 Wheat 43
Analyze and Conclude
1. Draw Conclusions Based on the hemoglobin data, which mammal listed is most closely related to humans? What is the evidence for your conclusion?
2. Analyze Data Does the cytochrome c data support your conclusion in Question 1? Explain.
3. Evaluate Does the data support the rankings you made as part of the pre-lab? If not, how would you explain any differences?
4. Design an Experiment The cytochrome c in both horses and pigeons differs from the human protein at 12 locations. Based on this data, you might infer that horses and pigeons are closely related. What could you do to support or refute this hypothesis?
5. Communicate In terms of descent, what does it mean to say that humans are more closely related to gorillas than to monkeys?
6. Interpret Data A student used the hemoglobin data (page 2) to conclude that mice and shrews are more closely related than are mice and humans or shrews and humans. Was the student correct? How do you know?
Extend Your Inquiry
More than 100 locations were not listed in Figure 1 because the amino acid was the same in all eight species. One possible explanation is that no mutations occurred in the codons for those locations. Suggest another possible explanation.
Name___________________________________________ Block________ Date____________
four protein chains. Figure 1 shows the amino acid sequence for one of those chains in eight mammals. Each letter stands for a different amino acid. Each column is a location on the protein chain. note: Locations where the amino acids are identical in all eight mammals are not shown.