A Pipe Cleaner Exercise to Illustrate Difficulties in DNA Replication to Students Investigating the Meselson-Stahl Experiment

 

Todd Nickle

Tested Studies in Laboratory Teaching, 2003, Volume 24

Abstract

When teaching the Meselson-Stahl experiment investigating DNA synthesis, some students discount the conservative and dispersive methods of replication without considering that they indeed once were valid models to investigate. The double-helix structure of DNA is exceedingly awkward to unwind in order for semiconservative replication to be carried out successfully. With our current understanding of the enzymes involved in DNA replication, we know the topoisomerases assist unwinding by breaking the sugar-phosphate backbone to relieve torsion. In this exercise, students will model the DNA strand using pipecleaners and work in pairs to see the rapid buildup of torsion that occurs when trying to separate them into single-stranded pieces. This exercise is done during a normal lecture and provides a kinesthetic experience demonstrating a physical property of the double-helix structure.

Keywords:  DNA replication

Louisiana State University (2002)