So we have adenine and we have guanine. So adenine is given by A and guanine is given by g and these are the two molecules. So we have two fused rings. So the difference between these two molecules is the presence of different types of groups. So in this particular case, we have this nitrogen containing group and in this case we have an H. In this case we have a nitroge containing group. But in this case we have a carbon oxygen double bond.