*
*

Back to teacher Home

NOVA scienceNOW: Bird Brains

Classroom Activity

Activity SummaryStudents will certainly compare the sequence of amino mountain in a gene shared in between humans and also six various other organisms and also infer evolution relationships among the species.

You are watching: Why do scientists study proteins to find evidence for evolution

Learning ObjectivesStudents will be maybe to:

explain that various organisms regularly have the same genes.

understand just how scientists use genetic distinctions to infer evolution relationships.

relate exactly how shared genes might be a an outcome of shared evolutionary history.

provide evidence suggesting that living things share usual ancestors.

Suggested TimeOne class period

*

BackgroundIn the NOVA scienceNOW segment Bird Brains, students learn that organisms as diverse as mushrooms, fish, flies, and humans re-publishing a gene dubbed FOXP2. This gene produce a form of protein called a warrior factor, i beg your pardon turns various other genes "on" or "off." Transcription components regulate numerous other genes, and because that this, they may affect multiple processes in different organisms. In animals, the FOXP2 gene is especially active during embryonic development in the brain, gut, heart, and also lungs, however scientists are still unraveling which gene it regulates in every of these tissues.

As described in the NOVA scienceNOW segment, FOXP2 also plays a role in the processes associated in human speech and also birdsong: civilization with one altered form of the gene have challenge with many aspects of speech, and birds whose FOXP2 task is disrupted have actually trouble finding out songs. Despite these and also other observations, researchers still don"t know which other genes FOXP2 regulates or what its role is in the numerous other types that share this gene through birds and humans. That FOXP2 is so widespread raises added questions, no only around its duty in other organisms, but also how the gene differs from one biology to the next.

All life ~ above Earth emerged from a single common ancestor, and our gene reflect this common ancestry. As varieties differentiated end evolutionary time, the DNA sequences in your genes acquired slight changes. Follow to evolutionary theory, these changes accumulate over time: varieties that diverged from each various other long ago have more differences in your DNA than varieties that diverged recently. Researchers use this level of difference as a molecular clock to aid them predict just how long ago varieties split except one another. In general, researchers say the longer earlier two types split, the an ext distantly connected they are.

You might need come remind your students around the nature of DNA, genes, proteins, and amino acids and how they different from one another. DNA is a molecule comprised of four varieties of units called bases. The four bases—adenine (A), cytosine (C), guanine (G) and also thymine (T)—collectively comprise the DNA "alphabet." Genes are distinctive locations follow me the length of a DNA molecule. The sequence of bases in a gene determines the stimulate of amino acids in a protein, and also the order of amino acids acts together the blueprint for protein assembly.

Because the DNA sequence determines a protein"s amino acid sequence, a gene common by two carefully related biology should have similar, or also identical, amino mountain sequences. That"s because closely related species most most likely diverged indigenous one another fairly recently in the evolutionary span. Thus, they haven"t had actually as lot time to accumulate random mutations in their hereditary codes.

For years, scientists have used DNA and also amino acid sequences to decipher relationships in between closely associated species, such as different species of reptiles, birds, and also even bacteria. The approach, called "molecular phylogeny," compares succession data and also ranks organisms" level of relatedness based on the distinctions in their DNA. As researchers sequence the genomes of an increasing variety of organisms every year, they uncover much more data to usage in evolution studies. In the emerging field of phylogenomics, researchers simultaneously compare many genes—and will one day compare finish genomes—to build brand-new evolutionary trees.

In this activity, her students will analyze a suite the amino acid sequences native a gene that provides the protein Cytochrome C. All eukaryotic organisms re-superstructure this protein, i beg your pardon plays a main role in the energy-producing process of to move respiration. Cytochrome C is an iron-containing molecule the carries electrons during the electron deliver chain in to move respiration. The protein is uncovered in plenty of lineages, consisting of those that animals, plants, and also numerous uncellular cells species. That ubiquity renders it a convenient tool for researching evolution. By counting the number of amino mountain differences between humans and also six various other species, her students will be able to make predictions about how closely related humans are to every species.

*
Before the Lesson
If necessary, testimonial the terms "DNA," "amino acid," "gene," and also "protein" with the class.The LessonLead a brief brainstorm session around how scientists classify organisms. What criteria can scientists usage to identify how very closely related two types are? They can look for similarity in physics features, behavior, mode of reproduction, or genes. Job-related through an instance as a class.Explain that each letter in the table Amino mountain in the Protein Cytochrome C to represent an amino mountain in the protein Cytochrome C. The an essential shows lock which amino acid corresponds to every letter. Speak to students" fist to the amino acid sequences because that humans and also tuna. Be sure students recognize that due to the fact that the sequence is too long to to the right on one heat of text, the wraps come a second line. Explain that they will look because that the number of amino acids that differ between humans and also tuna. Additionally explain that plain-text letters represent amino mountain that may vary between species, while letter in bold space amino acids the are the same in all species. First, counting the number of differences in the succession together. The an initial difference is at position 17; humans have an "I," while tuna have a "T." Be certain all students can identify the 21 differences between humans and also tuna.Have students complete the handouts.To plunder up, comment on the complying with points together a class:The table perform three types of fungi: Candida, Neurospora, and baker"s yeast. How comparable are their Cytochrome C sequences? their sequences are rather different, with 41 differences in between neurospora and baker"s yeast, 43 between neurospora and Candida, and 27 in between baker"s yeast and Candida. What can you say around the evolution relationships amongst the fungi compared to the relationship in between the 2 insects on the table, the screwworm fly and the silkworm moth? The fly and the moth are an ext closely related in evolutionary time; there are only 14 differences in between the fly and moth Cytochrome C sequences.Pigs, cows, and also sheep have identical Cytochrome C sequences. How have the right to they have the exact same sequence yet be various species? The difference between types is identified by numerous factors; different varieties can still have actually identical sequences, specifically if they diverged from a typical ancestor recently in evolutionary time. Is it proper for researchers to infer evolutionary relationships based on information from only one protein? Why or why not? These animals each have actually thousands the genes. The reality that one gene is the same for the three animals says nothing about the various other genes. It"s far better to look in ~ multiple proteins or other sources the DNA evidence. Proteins evolve at various rates, and extr pieces of evidence will do a prediction around an evolutionary partnership stronger.Extension

Divide the class into four teams. Assign each team among the following genes: FOXP2, hemoglobin alpha, eyeless, and also sonic hedgehog. Have students visit the Kyoto Encyclopedia the Genes and also Genomes and also look up your gene"s amino mountain sequence in humans. Have actually students research study how plenty of of the six varieties from their handouts re-publishing this gene through humans; because that all situations in which species share the gene, have actually students compose down the an initial ten amino acids listed in the database. Then have students prepare a brief report around the gene, just how much similarity lock discovered in between humans and also other species, and what scientists know around the gene"s function.

ASSESSMENTActivity answers:Human-tuna: ____21___Human: gray whale ___9____Human: snapping turtle: ____15___Human-rhesus monkey: ___1__Human: chicken/turkey: ___13____Human: neurospora (a type of bread mold): __51_______

Student Handout QuestionsBased ~ above the amino acid sequence data girlfriend collected, which biology are people most very closely related to? Which organisms are humans most distantly related to? define your reasoning. humans are most carefully related come the monkey; over there is just one amino mountain difference in between the two. Human beings are most distantly concerned Neurospora; there are 51 amino acid differences between the two.What added data or details might assist you check the statement friend made above? information from various other genes would strengthen the statement; we also could usage fossil proof or physical proof such as similarity in physical structures and also features.Does your answer to concern 1 over match the prediction girlfriend made in step 2 of the Procedure? describe your answer.Answers will vary; look for evidence that student compare your answers and explain why they room the same, or why they space different. Describe how amino mountain sequence data can assist scientists infer fads of evolution relationships in between species. One amino acid is one of the structure blocks that a protein. A gene"s DNA sequence determines the order of amino acids that make up a protein, so alters in the DNA sequence often result in changes in the amino acid sequence as well. By trying to find amino mountain sequence differences in between species, scientists deserve to infer how carefully or distantly connected two species are in evolutionary time.

Use the adhering to rubric come assess every team"s work.

ExcellentSatisfactoryNeeds improvement
Completing handouts and participating in discussionStudents plainly understand how molecular evidence relates to inferring fads of evolutionStudents questioning follow-up inquiries showing creative thinking and an important thinkingStudents miscount amino acid distinction between species and execute not do a connection in between molecular evidence and also patterns of evolutionStudents make small effort to complete handouts or take part in discussion.
*

The "Bird Brains" task aligns through the following National Science education Standards (see books.nap.edu/html/nses).

Grades 9-12Content typical CLife ScienceMolecular basis of heredity

Content typical FScience in personal and society PerspectivesPersonal and Community Health

Classroom activity Author

Jennifer Cutraro and WGBH educational Outreach Staff

Jennifer Cutraro has 12 years of endure in science writing and education. She has actually written text and also ancillaries for Houghton Mifflin, K12, and Delta Education and has teach science and also environmental education and learning at scientific research centers throughout the country. She additionally contributes news and feature stories around science and health come media outlets consisting of The Los Angeles Times, The Boston Globe, science News because that Kids and Scholastic science World.

*
*

NOVA scienceNOW: Bird Brains

*

Original broadcast:July 16, 2008

*
*
*
*
*
*
*
Bird brains QuickTime or home windows Media segment
Biology: Molecular differences speed Animation
*

Funding for NOVA scienceNOW is noted by Pfizer, the national Science Foundation, the Howard Hughes medical Institute, the Alfred P. Sloan Foundation, and public television viewers.

See more: Is Optimus Prime And Megatron Brothers ? Optimus Prime

*
*
*
*
A private corporation sponsor by the American people

This product is based upon occupational supported by the nationwide Science structure under grant no. 0638931. Any type of opinions, findings, and also conclusions or recommendations expressed in this material are those that the author(s) and do not necssarily reflect the views of the nationwide Science Foundation.