But in the past, obstacles have plagued the development of such a map for cannabis. Legislation has barred researchers from readily studying and experimenting with the plant, even in controlled laboratory settings. On top of that, it’s inherently difficult to map the cannabis genome, thanks to its relatively large size. The larger the genome, the harder it is to categorize, which is why it took so long for scientists to map and make sense of the human genome. The difficulty in sequencing and assembling the cannabis genome was compounded by the viral elements. See, both THC and CBD are made by synthase genes that are found on the same chromosome. But those synthase genes are swarmed by garbled chunks of DNA called retrotransposons, which came from—you guessed it—viruses. Over time, those millions of infectious DNA elements multiplied and spread throughout the genome. The THC and CBD synthase genes are firmly nested in those elements.