DNA contains the genetic information in cells, but proteins are not made directly from DNA. Instead, complementary RNA molecules must first be made from the DNA. The process of making RNA from DNA is called transcription. As shown schematically in Figure 4.21, transcription requires an enzyme called RNA polymerase.

The base pairing rules for making RNA from DNA are the following:

1. T in DNA is transcribed as A in RNA

2. G in DNA is transcribed as C in RNA

3. A in DNA is transcribed as U in RNA

4. C in DNA is transcribed as G in RNA