We begin our detailed study of transcription by looking at the synthesis and processing of mRNAs, the molecules that make up the transcriptome and which specify the protein content of the cell.

DNA transcription, also known as RNA synthesis is the process by which genetic information that is contained in DNA is re-written into messenger RNA (mRNA) by an RNA polymerase enzyme. The synthesized mRNA is transported out of the cell nucleus where it will later on aid in the synthesis of proteins by the mechanism of translation.

RNA is synthesized from its 5′ end to its 3′ end, antiparallel to its DNA template strand (see p. 463). The template is copied as it is in DNA synthesis, in which a guanine (G) on the DNA species a cytosine (C) in the RNA , a C species a G, a T species an A , but an A species a U instead of a T (Fig. 31. 5). The RNA , then, is

DNA transcription is the process of copying genetic information from DNA to RNA. It involves the synthesis of RNA molecules using a DNA template and is an essential step in gene expression and protein synthesis.

In eukaryotic cells, RNA synthesis, which occurs in the nucleus, is separated from the protein synthesis machinery, which is in the cytoplasm. In addition, eukaryotic genes have introns, noncoding regions that interrupt the gene’s coding sequence.