At that time, it was unclear how this simple molecule could hold all the complex information controlling the development of humans, animals and plants. Scientists knew it was made of four chemical bases called [[adenine]] (A), [[thymine]] (T), [[guanine]] (G) and [[cytosine]] (C), plus [[phosphoric acid]] and a [[sugar]]. They also knew that the ratios of A and T as well as G and C were always the same, but they did not know the rules that controlled the arrangement. | At that time, it was unclear how this simple molecule could hold all the complex information controlling the development of humans, animals and plants. Scientists knew it was made of four chemical bases called [[adenine]] (A), [[thymine]] (T), [[guanine]] (G) and [[cytosine]] (C), plus [[phosphoric acid]] and a [[sugar]]. They also knew that the ratios of A and T as well as G and C were always the same, but they did not know the rules that controlled the arrangement. |