We discussed how to purify proteins and also how to sequence proteins. But where do proteins actually come from? In the next 20 or so lectures, we're going to focus on nucleic acids because it's the nucleic acids that essentially are used to build these proteins. So what types of nucleic acids do we have inside our body? So we have two types. We have deoxyribonucleic acids or DNA molecules and we have ribonucleic acids or RNA molecules.