Transcription is the process of creating a complimentary strand of RNA copy from a corresponding DNA sequence. Both RNA and DNA are nucleic acids which are base pairs of nucleotides in a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes. During transcription, a DNA sequence is read by an RNA polymerase which produces a complimentary antiparallel RNA strand. As opposed to DNA replication, transcription results in an RNA complement that includes uracil (U) in all instances where thymine (T) would have occured in a DNA complement. Transcription progresses like this:
1. DNA unwinds/unzips, as the hydrogen bonds break.
2. The free nucleotides of RNA pair with complementary DNA bases.
3. RNA sugar-phosphate backbone forms.
4. Hydorogen bonds of the untwisted RNA + DNA ladder break, freeing up new RNA.
5. If the cell has a nucleus, the RNA is further processed and then moves through the small nuclear pores into the cytoplasm of the cell.