1. Unwinding and Separation:
* The DNA double helix unwinds and separates at a specific location called the promoter region. This region contains a sequence of nucleotides recognized by RNA polymerase, the enzyme responsible for transcription.
2. RNA Polymerase Binding:
* RNA polymerase binds to the promoter region and initiates transcription.
3. RNA Synthesis:
* RNA polymerase moves along the DNA template strand, using it as a guide to synthesize a complementary RNA molecule.
* Instead of thymine (T), RNA uses uracil (U).
* The RNA molecule synthesized is called messenger RNA (mRNA).
4. Termination:
* Transcription continues until RNA polymerase reaches a specific signal called the terminator sequence.
* At this point, the RNA polymerase detaches from the DNA template, and the newly synthesized mRNA molecule is released.
5. mRNA Processing:
* The mRNA molecule undergoes several processing steps before it can be translated into protein:
* Capping: A modified guanine nucleotide (5' cap) is added to the 5' end of the mRNA molecule.
* Splicing: Non-coding regions called introns are removed, and the coding regions called exons are spliced together.
* Polyadenylation: A string of adenine nucleotides (poly-A tail) is added to the 3' end of the mRNA molecule.
Summary:
DNA serves as a template for the synthesis of mRNA, which carries the genetic information from the nucleus to the ribosomes in the cytoplasm where protein synthesis takes place. This process of transcription is crucial for gene expression and protein synthesis.
