Case Study of Cystic Fibrosis

In today’s lesson, we used a case study about cystic fibrosis as the mechanism to:

  • review the stop codon;
  • connect the concepts of protein structure and function;
  • review how R groups differentiate amino acids;
  • review how R group interactions result in protein folding;
  • discuss “structure equals function”;
  • bring a human face to a genetic disease;
  • and help students recall the mechanism of genetic inheritance.

For the entry task, students were challenged to consider how genes begin and end.  We discussed how mRNA sequences always begin with AUG (which codes for methionine, and amino acid which may also occur elsewhere in a protein).  Students were then reminded of the three “stop codons” and we reviewed how those work to release a protein from the ribosome.  We reviewed the structure of amino acids, focusing on the 20 different R groups and how those R groups each have different properties.  The interactions between R groups determine protein shape, and shape determines protein function.  When the sequence changes, the shape changes, thus changing the function of a protein.  We then moved into the cystic fibrosis case study, first watching the video below and then working through the lesson PowerPoint.

Class concluded with a few additional notes, pictured below:

Mirror-Image Isomers

We began with the Lesson 47 PowerPoint ChemCatalyst to help get students thinking about mirror images.  We then watched a short video about chirality (below):

Students then received the Lesson 47 Worksheet, working in pairs to model the compounds using the class set of molecular modeling kits.  The worksheet concluded with students hypothesizing whether L-carvone will smell like D-carvone, and then testing their hypothesis.  For homework, students were assigned textbook questions 5-8.

Update: January 18

Given the challenging nature of the subject matter in Lesson 47, we used most of the class period to review the homework, build molecules, and discuss the relationship between isomers and chirality.  Notes from the overhead are shown below:

Want more?  Check out the blog post Perhaps looking-glass milk isn’t good to drink for an overview of Lewis Carroll, looking-glass milk, and L- and D-carvone.  Want more?  Joanna Shawn Brigid O’Leary from Rice University published an even more extensive investigation of how Lewis Carroll (author of Alice in Wonderland and Through the Looking Glass) weaved biochemistry into his fiction.  Her paper (available as a PDF), WHERE ‘THINGS GO THE OTHER WAY’: THE STEREOCHEMISTRY OF LEWIS CARROLL’S LOOKING-GLASS WORLD is well worth the read.  Perhaps it will even inspire students to read the book before the movie is released in theaters on May 27!