Similarity In Amino Acids Between Animals Is An Example Of What Kind Of Evolutionary Evidence?

NOVA scienceNOW: Bird Brains

Classroom Activity

Activity Summary
Students will compare the sequence of amino acids in a gene shared betwixt humans and six other organisms and infer evolutionary relationships amid the species.

Learning Objectives
Students will be able to:

explain that different organisms often have the aforementioned genes.
understand how scientists use genetic differences to infer evolutionary relationships.
chronicle how shared genes may be a result of shared evolutionary history.
provide bear witness suggesting that living things share mutual ancestors.

Suggested Time
One course period

Predicting Evolutionary Relationships Educatee Handout (PDF)

Groundwork
In the NOVA scienceNOW segment Bird Brains, students larn that organisms as diverse as mushrooms, fish, flies, and humans share a gene called FOXP2. This gene produces a blazon of protein called a transcription factor, which turns other genes "on" or "off." Transcription factors regulate many other genes, and because of this, they may affect multiple processes in unlike organisms. In animals, the FOXP2 gene is especially agile during embryonic evolution in the brain, gut, heart, and lungs, but scientists are still unraveling which genes it regulates in each of these tissues.

As explained in the NOVA scienceNOW segment, FOXP2 as well plays a role in the processes involved in homo speech and birdsong: people with an altered grade of the cistron have difficulty with many aspects of oral communication, and birds whose FOXP2 activeness is disrupted have trouble learning songs. Despite these and other observations, scientists withal don't know which other genes FOXP2 regulates or what its role is in the numerous other species that share this gene with birds and humans. That FOXP2 is so widespread raises additional questions, not just nigh its part in other organisms, but also how the gene differs from ane organism to the next.

All life on Earth arose from a single common antecedent, and our genes reflect this shared ancestry. As species differentiated over evolutionary fourth dimension, the DNA sequences in their genes acquired slight changes. According to evolutionary theory, these changes accrue over time: species that diverged from each other long agone take more differences in their Dna than species that diverged recently. Scientists use this caste of deviation as a molecular clock to help them predict how long ago species split apart from one another. In full general, scientists say the longer ago two species split, the more distantly related they are.

You may need to remind your students well-nigh the nature of DNA, genes, proteins, and amino acids and how they differ from one another. Deoxyribonucleic acid is a molecule made upward of four types of units called bases. The 4 bases—adenine (A), cytosine (C), guanine (Thousand) and thymine (T)—collectively make up the Dna "alphabet." Genes are singled-out locations along the length of a DNA molecule. The sequence of bases in a gene determines the gild of amino acids in a protein, and the lodge of amino acids acts as the blueprint for protein assembly.

Because the Deoxyribonucleic acid sequence determines a poly peptide's amino acid sequence, a gene shared by two closely related organisms should have similar, or even identical, amino acid sequences. That's because closely related species almost probable diverged from one another fairly recently in the evolutionary span. Thus, they haven't had equally much time to accumulate random mutations in their genetic codes.

For years, scientists have used DNA and amino acid sequences to decipher relationships between closely related species, such as different types of reptiles, birds, and even bacteria. The approach, called "molecular phylogeny," compares sequence data and ranks organisms' degree of relatedness based on the differences in their Deoxyribonucleic acid. As researchers sequence the genomes of an increasing number of organisms every year, they uncover more data to use in evolutionary studies. In the emerging field of phylogenomics, researchers simultaneously compare numerous genes—and will i day compare complete genomes—to build new evolutionary trees.

In this activity, your students will clarify a suite of amino acid sequences from a gene that makes the protein Cytochrome C. All eukaryotic organisms share this protein, which plays a central function in the free energy-producing procedure of cellular respiration. Cytochrome C is an iron-containing molecule that carries electrons during the electron ship chain in cellular respiration. The poly peptide is found in many lineages, including those of animals, plants, and numerous unicellular species. Its ubiquity makes it a convenient tool for studying evolution. By counting the number of amino acrid differences between humans and half dozen other species, your students volition be able to make predictions about how closely related humans are to each species.

Before the Lesson

Bookmark the Web sites Bird Brains and Biology: Molecular Differences.
Prepare enough copies of the Predicting Evolutionary Relationships educatee handout so that each pupil volition accept ane.
As a form, watch the NOVA scienceNOW segment Bird Brains.
If necessary, review the terms "DNA," "amino acid," "gene," and "protein" with the course.

The Lesson

Lead a brusk brainstorm session about how scientists classify organisms. What criteria might scientists use to determine how closely related 2 species are? They might look for similarity in concrete features, beliefs, manner of reproduction, or genes.
Introduce the concept of using molecular evidence, such as DNA or amino acid sequence data, to unravel evolutionary relationships between species (run into groundwork). You lot might point out that for some species, physical traits solitary don't offer enough clues. For example, is a horse more than closely related to a dog or to a buffalo? All iii have fur and walk on four legs, but these clues don't tell you much about evolution. Optional: If possible, show the curt blitheness Biological science: Molecular Differences. Inquire students what boosted data Deoxyribonucleic acid evidence provides scientists studying evolution.
Divide the class into pairs and distribute the Predicting Evolutionary Relationships handout.
Work through an example as a class.
- Explain that each letter in the table Amino Acids in the Protein Cytochrome C represents an amino acid in the protein Cytochrome C. The central shows them which amino acid corresponds to each letter.
- Telephone call students' attention to the amino acrid sequences for humans and tuna. Be sure students empathize that considering the sequence is too long to fit on one line of text, it wraps to a 2d line. Explain that they will look for the number of amino acids that differ betwixt humans and tuna. Also explain that plain-text messages represent amino acids that may vary between species, while letters in bold are amino acids that are identical in all species.
- Start, count the number of differences in the sequence together. The offset difference is at position 17; humans take an "I," while tuna have a "T." Be sure all students can place the 21 differences between humans and tuna.
Have students complete the handouts.
To wrap up, discuss the following points as a course:
- The table lists three species of fungi: Candida, Neurospora, and baker's yeast. How similar are their Cytochrome C sequences? Their sequences are quite unlike, with 41 differences between neurospora and bakery's yeast, 43 between neurospora and Candida, and 27 between baker'southward yeast and Candida. What tin y'all say nigh the evolutionary relationships among the fungi compared to the relationship betwixt the two insects on the table, the screwworm fly and the silkworm moth? The fly and the moth are more closely related in evolutionary time; at that place are just 14 differences between the fly and moth Cytochrome C sequences.
- Pigs, cows, and sheep accept identical Cytochrome C sequences. How tin can they have the aforementioned sequence simply be unlike species? The departure betwixt species is determined past many factors; different species can nevertheless take identical sequences, especially if they diverged from a common ancestor recently in evolutionary time.
- Is it appropriate for scientists to infer evolutionary relationships based on information from only one protein? Why or why non? These animals each have thousands of genes. The fact that i factor is identical for the 3 animals says cipher about the other genes. It'south better to expect at multiple proteins or other sources of DNA evidence. Proteins evolve at different rates, and additional pieces of evidence volition make a prediction about an evolutionary relationship stronger.

Extension

Separate the form into four teams. Assign each squad 1 of the following genes: FOXP2, hemoglobin blastoff, eyeless, and sonic hedgehog. Take students visit the Kyoto Encyclopedia of Genes and Genomes and look upwardly their gene's amino acid sequence in humans. Have students research how many of the six species from their handouts share this gene with humans; for all cases in which species share the factor, have students write down the start ten amino acids listed in the database. And then have students prepare a short report about the cistron, how much similarity they discovered between humans and other species, and what scientists know most the gene'due south function.

Assessment
Action answers:
Man-tuna: ____21___
Homo: grey whale ___9____
Homo: snapping turtle: ____15___
Homo-rhesus monkey: ___1__
Human: chicken/turkey: ___13____
Human: neurospora (a blazon of bread mold): __51_______

Student Handout Questions

Based on the amino acrid sequence information you collected, which organism are humans most closely related to? Which organisms are humans nearly distantly related to? Explain your reasoning.
Humans are about closely related to the monkey; there is only i amino acid difference between the 2. Humans are most distantly related to Neurospora; there are 51 amino acid differences between the two.
What additional data or information might help you confirm the argument you made above?
Data from other genes would strengthen the statement; we also could use fossil evidence or physical evidence such equally similarity in concrete structures and features.
Does your answer to Question one in a higher place friction match the prediction you fabricated in Step 2 of the Procedure? Explain your answer.
Answers will vary; await for evidence that students compare their answers and explain why they are the same, or why they are different.
Explicate how amino acid sequence data tin can help scientists infer patterns of evolutionary relationships between species.
An amino acid is one of the edifice blocks of a protein. A gene's DNA sequence determines the order of amino acids that make up a poly peptide, so changes in the DNA sequence oftentimes outcome in changes in the amino acid sequence as well. By looking for amino acid sequence differences between species, scientists tin can infer how closely or distantly related two species are in evolutionary fourth dimension.

Use the following rubric to assess each squad's work.

	Excellent	Satisfactory	Needs improvement
Completing handouts and participating in discussion	Students conspicuously sympathize how molecular bear witness relates to inferring patterns of development Students ask follow-upward questions showing inventiveness and critical thinking	Students miscount amino acid divergence between species and do not make a connection between molecular show and patterns of development	Students brand trivial attempt to complete handouts or participate in discussion.

The "Bird Brains" action aligns with the following National Scientific discipline Education Standards (see books.nap.edu/html/nses).

Grades 9-12
Content Standard C
Life Science

Molecular basis of heredity

Content Standard F
Science in Personal and Social Perspectives

Personal and Community Wellness

Classroom Activity Author

Jennifer Cutraro and WGBH Educational Outreach Staff

Jennifer Cutraro has 12 years of feel in science writing and education. She has written text and ancillaries for Houghton Mifflin, Chiliad¹², and Delta Education and has taught science and environmental pedagogy at scientific discipline centers beyond the country. She as well contributes news and feature stories near science and health to media outlets including The Los Angeles Times, The Boston World, Scientific discipline News for Kids and Scholastic Scientific discipline World.

Funding for NOVA scienceNOW is provided past Pfizer, the National Scientific discipline Foundation, the Howard Hughes Medical Constitute, the Alfred P. Sloan Foundation, and public television viewers.

A private corporation funded by the American people

This textile is based upon work supported past the National Science Foundation under Grant no. 0638931. Whatever opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necssarily reverberate the views of the National Science Foundation.

Source: https://www.pbs.org/wgbh/nova/teachers/activities/0304_01_nsn.html

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