Ok while I know this isn't officially confirmed, this is just a theory I have. Rayquaza is the RNA to Deoxys's DNA. I say this because Rayquaza, just like RNA, isn't in a double helix like DNA and Deoxys's arms, Rayquaza is a long serpentine pokemon just like how RNA is long and straight. Additionally, Rayquaza's name starts with R which is what RNA starts with.