Pre Lab: Amino Acid Sequences: Indicators of Evolution
Problem How can you use proteins to determine how closely organisms are related?
Materials light-colored highlighting pen; graph paper
Lab Manual Chapter 16 Lab
Skills Analyze Data, Graph, Draw Conclusions
Connect to the For years, scientists who studied evolution had to rely on only visible differences among organisms. Then a new source of evidence emerged. Biochemists were able to unravel the sequences of bases in DNA and amino acids in proteins. Scientists are able to use these data to confirm relationships based on anatomy. They also use the data to show that some species that appear very different are in fact more closely related than had been thought.
Biologists can compare the sequences of amino acids in a protein for two species. In general, when the total number of differences is small, the species are closely related. When the total number of differences is large, the species are more distantly related.
In this lab, you will compare amino acid sequences for one protein and analyze the results of a similar comparison for another protein. You will use both sets of data to predict relatedness among organisms.
Review What are homologous molecules?
Explain Why might scientists use molecules instead of anatomy to figure out how closely rabbits and fruit flies are related?
Relate Cause and Effect Amino acid sequences in the proteins of two species are similar. What can you conclude about the DNA in those species, and why?
Preview the procedure in the lab manual.
Predict Based only on their anatomy, rank gorillas, bears, chimpanzees, and mice from most recent common ancestor with humans to least recent.
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. Overtime, the number of changes increases. How is this process an analogy for what happens to DNA over time?
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,” and why?
Visit Chapter 16 online to test yourself on chapter content and to find activities to help you learn.
Untamed Science Video Islands are rich envi-ronments for evolution, as you will find out with the Untamed Science crew.
Art in Motion This animation shows how fossil layers accumulate and are later exposed.
Art Review Review homologous and analogous structures in vertebrates.
Visual Analogy See how different types of finch beaks function like tools.
Data Analysis Collect population data for several generations of grasshoppers and then analyze how the population changed due to natural selection.