mention the main features of transcription process
Answers
Answer:
Transcription is divided into initiation, promoter escape, elongation, and termination.
Initiation.
Promoter escape.
Elongation.
Termination.
Transcription, the synthesis of RNA from DNA. Genetic information flows from DNA into protein, the substance that gives an organism its form. This flow of information occurs through the sequential processes of transcription (DNA to RNA) and translation (RNA to protein). Transcription occurs when there is a need for a particular gene product at a specific time or in a specific tissue.
During transcription, only one strand of DNA is usually copied. This is called the template strand, and the RNA molecules produced are single-stranded messenger RNAs (mRNAs). The DNA strand that would correspond to the mRNA is called the coding or sense strand. In eukaryotes (organisms that possess a nucleus) the initial product of transcription is called a pre-mRNA. Pre-mRNA is extensively edited through splicing before the mature mRNA is produced and ready for translation by the ribosome, the cellular organelle that serves as the site of protein synthesis. Transcription of any one gene takes place at the chromosomal location of that gene, which is a relatively short segment of the chromosome. The active transcription of a gene depends on the need for the activity of that particular gene in a specific cell or tissue.
Small segments of DNA are transcribed into RNA by the enzyme RNA polymerase, which achieves this copying in a strictly controlled process. The first step is to recognize a specific sequence on DNA called a promoter that signifies the start of the gene. The two strands of DNA become separated at this point, and RNA polymerase begins copying from a specific point on one strand of the DNA using a special type of sugar-containing nucleoside called ribonucleoside 5’-triphosphate to begin the growing chain. Additional ribonucleoside triphosphates are used as the substrate, and, by cleavage of their high-energy phosphate bond, ribonucleoside monophosphates are incorporated into the growing RNA chain. Each successive ribonucleotide is directed by the complementary base pairing rules of DNA. For example, a C (cytosine) in DNA directs the incorporation of a G (guanine) into RNA. Likewise, a G in DNA is copied into a C in RNA, a T (thymine) into an A (adenine), and an A into a U (uracil; RNA contains U in place of the T of DNA). Synthesis continues until a termination signal is reached, at which point the RNA polymerase drops off the DNA, and the RNA molecule is released.