Answer: DNA and RNA
DNA (deoxyribonucleic acid) is a molecule made up of two chains that coil around each other and carries the genetic instructions of all known living organisms. On the other hand, RNA (ribonucleic acid) is a polymeric molecule basic for coding, decoding, regulation and expression of genes.
The game states that DNA and RNA have no direct relationship, but collaborate. The "expression" refers to gene expression.