Transcription is the process by which a particular DNA sequence (e.g., a gene) is used as a template to synthesize a complementary RNA sequence that grows in a 5′ → 3′ direction. This RNA molecule is usually a messenger RNA (mRNA) which is then used to synthesize a polypeptide chain (i.e., a protein) by a process called translation. The complementary RNA molecule produced during transcription is synthesized according to the base pair rules, i.e., Adenine (A) bases always pair with Thymine (T) bases, while Guanine (G) bases always pairs with Cytosine (C) bases. In RNA, Uracil (U) bases pair with adenine, thereby replacing thymines during transcription.
