What Happened to Beau?
How Amino Acids Affect Keratin Organization in Hair
Wake Forest University
This flipped case was designed to introduce students in a general introductory biology course to basic protein structure. The two videos and interrupted case use keratins in hair as model proteins. From the videos students learn how amino acids regulate protein structure, and how small changes in amino acid sequence have large impacts on overall protein organization and function. The case story focuses on a puppy whose hair changes from straight to curly when it sheds its coat. The protagonist tests the adult versus puppy hair, and discovers that the amino acid composition is different in the curly versus straight hair samples. Students apply basic principles of protein structure to hypothesize why the dog's coat switched from straight to curly. The case intentionally stops short of providing a complete answer to the mystery, so students think through the molecular processes logically rather than having a final "correct" answer. An optional activity is provided that makes the case more appropriate for an introductory cell biology class.
- Learn basic properties of proteins, e.g., that the shape of a protein is determined by molecular interaction forces, which are in turn defined by amino acid sequences.
- Practice identifying patterns in tabulated data.
- Correlate physical and biochemical evidence with descriptive observations.
- Make provisional hypotheses, then revise or eliminate them based on subsequent evidence.
Keywordsprotein; protein structure; amino acid; keratin; peptide; hair; curly; folding;
Educational LevelUndergraduate lower division
Type / MethodsDiscussion, Flipped, Interrupted
Subject HeadingsBiology (General) | Cell Biology |
The optional supplemental material below is recommended for use with this case study.A Decade After the Genome, Scientists Map the "Proteome"
Mapping Genes to Traits in Dogs Using SNPs
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The following video(s) are recommended for use in association with this case study.
- Protein Structure, Part 1: Where Are Proteins? What Do They Do?
This video leads students through an overview of general protein structure, with emphasis on keratin. Students learn that proteins are composed of 20 different amino acids and that the sequence of amino acids gives each protein its unique properties. Running time: 5:35 min. Created by A. Daniel Johnson for the National Center for Case Study Teaching in Science, 2016.
- Protein Structure, Part 2: How and Why Do Proteins Fold Into Complex Shapes?
This video explores the role of amino acid sequence in protein structure, how hydrogen bonding of the peptide backbone creates the secondary structure of proteins, and how intra- and intermolecular interactions define tertiary and quaternary structure respectively. Students also learn how keratins are assembled in hair. Running time: 12:28 min. Created by A. Daniel Johnson for the National Center for Case Study Teaching in Science, 2016.
- Dog Breeding
This short video discusses how the many forms of dogs that exist today were all created through selective breeding from the dog's ancestor, the wolf. In a span of less than 10,000 years, breeders have changed traits and body shapes of dogs by artificial selection. For example, emphasizing different aspects of hunting and herding behavior. Produced by HHMI BioInteractive. Running time: 1:53 min.
- Dog Genomics and Dogs as Model Organisms
In this video lecture, Dr. Elinor Karlsson of the Broad Institute discusses using dogs in genome-wide association studies (GWAS), and the genetic evidence for dog domestication, as revealed by copy-number variations in the amylase gene. Produced by HHMI BioInteractive. Running time: 29 min.