RNA transcription is the process by which some information from a gene — contained in DNA of a cell's nucleus — is transcribed into RNA. The process occurs in all organisms, but there are significant differences between the way it works in bacteria and in most other cells. Transcription begins with a certain strand of the DNA double helix being unwound and attached, by a special enzyme, to a newly formed sequence of RNA. When all of the necessary information has been copied to the RNA, the molecule is then moved out of the cell's nucleus and used to manufacture a new protein.
DNA serves as the template for the information that cells need to make proteins, the building blocks of living tissues. RNA transcription is the process by which RNA is synthesized from DNA. It follows a somewhat different pathway in bacterial or prokaryotic cells than in most other cells found in plants and animals, called eukaryotes. Nevertheless, the basic steps of transcription occur in a few phases in all types of cells. These include initiation, elongation, and termination.
RNA transcription initiation starts when the enzyme RNA polymerase binds to the double helix of DNA and unwinds it in whatever region of DNA must be transcribed. Once there is a single-stranded segment of DNA opened up, the RNA polymerase begins matching the RNA base pairs to those of the DNA sequence being copied. The region of DNA to which RNA polymerase binds is called the promoter region. Elongation involves the addition of nucleotides, the specialized sugar containing molecules that make up DNA and RNA, in sequential order along the gene that is being transcribed.
The DNA bases are paired up with the appropriate RNA nucleotides in a process that is sometimes prone to errors, since there are many places where a code can be miscopied. Various proteins, called transcription factors, facilitate the transcription of DNA code into RNA and assist in guiding the base by base copying. RNA transcription also involves the construction of a support structure to hold the newly built RNA sequence together. This is called a sugar-phosphate backbone, and when it is formed, the bonds holding DNA and RNA together can then be broken, since the RNA is complete.
When termination occurs, the necessary RNA transcript separates from the DNA template and is ready for further processing in the cytoplasm of the cell. Gene expression is the process by which a specific gene is manufactured into a protein. RNA transcription is only the first step toward gene expression, occurring in the nucleus of a cell. Translation, the second step, occurs in the cell after the RNA passes out of the nucleus and is used to assemble a protein in the cell's cytoplasm.
