In this activity, students construct models of sickle cell hemoglobin fibers inside red blood cells to illustrate how changes in the structure of a protein can affect cell shape, as described in the short film The Making of the Fittest: Natural Selection in Humans.

Students step through a procedure for constructing paper models of wild type and mutant hemoglobin molecules. They build mutant hemoglobin fibers to show how these cause red blood cells to take on a different two-dimensional shape. Students then answer questions to explain how these changes in protein and cell structure relate to disease symptoms.