If this is adenine, this must be uracil. And if this is thymine, then this must be adenine, and so forth. So basically, when in the nucleus transcription takes place, the cell has no problem transcribing from our DNA to our RNA, because all it has to do is find the complementary nucleotide. But during the process of translation, when we synthesize our proteins from RNA molecules, things aren't that simple. And that's because our mRNA consists of nucleotides. So the language of RNA is the language of nucleotides, but proteins use the language of amino acids.