During transcription, information from DNA is copied onto mRNA in the nucleus. The enzyme responsible for this process is called RNA polymerase, and not DNA polymerase.
It is during DNA replication that DNA polymerase is involved. DNA replication is the process by which a new copy of DNA is made from the old copy.
Transcription occurs with the sole purpose of protein synthesis. After the information on DNA has been transcribed on mRNA with help of RNA polymerase, mRNA leaves the nucleus and enters the cytoplasm where it attaches to a ribosome. tRNA or transfer RNA then reads (translates) the coded information on the attached mRNA, fetches amino acids that correspond to this information and bring them to the ribosome where they are linked together to form the primary structure of the protein.
