This particular area of genetics can be quite complex. So basically in DNA their is adenine, cytosine, guanine, thymine. So, then there is another step to this: Adenine links with Thymine (A is to T), and Cytosine pairs up with Guanine (C is to G). This is known as base pairing. However, when translating DNA to RNA their is a catch, there is no thymine in RNA. Instead there is Uracil. SO in RNA it would be like so: A is to U and C is to G. So when transcribing DNA to mRNA it would be like this. I will give an example: DNA: TGA GTC AAT GGC. However with RNA it would be like this, using the same example I just showed you: ACU CAG UUA CCG. Do you see I it now? Basically when transcribing to RNA you use the opposite of all of the original copy except use Uracil instead of Thmine.
