Key points for Chapter 6 1. Definitions: topoisomerases ribozyme, double helix, DNA denaturation, Tm, linking number, pseudoknot. 2 What are the structural differences between dna and rna? how the structural properties of dNA and rna determine their distinct biological functions.Key points for Chapter 6 1.Definitions: topoisomerase, ribozyme, double helix, DNA denaturation, Tm, linking number, pseudoknot. 2.What are the structural differences between DNA and RNA? How the structural properties of DNA and RNA determine their distinct biological functions