Transcription is the process by which the D.N.A. instructions, which are in the nucleus, are copied or transcribed by R.N.A. The D.N.A. information remains in the nucleus, however, it can serve as a template for the R.N.A. to copy. The mRNA makes a complementary message to the DNA instructions. There are base pairing rules. RNA has the bases Adenine, Uracil, Cytosine and Guanine. Base pairing rules for RNA are if the D.N.A. has the base Adenine, the complementary RNA base is Uracil. If the base is cytosine, the complement in the RNA is guanine. If the base in the DNA is Thymine, the base adenine is the complementary RNA base. If the DNA has the base guanine, the RNA complement will be cystosine. Once the R.N.A. copies the genetic code, it can pass from the nucleus to the cytoplasm, and attaches to a ribosome. It is here, that transfer R.N.A. will help translate the message and produce the necessary proteins the cell needs in order to function properly.