Q. Concerning their biological function what is the difference between DNA and RNA?
DNA is the source of information for RNA production (transcription) and thus for protein synthesis. DNA is still the basis of heredity due to its replication capability.
The messenger RNA is the template for protein synthesis (translation). In this process tRNA and rRNA also participate since the first carries amino acids for the polypeptide chain formation and the second is a structural constituent of ribosomes (the organelles where proteins are made).