1. Unwinding and Separating DNA: The DNA double helix unwinds and separates into two strands. Only one of these strands will be used as a template for RNA synthesis.
2. Binding of RNA Polymerase: An enzyme called RNA polymerase binds to a specific region on the DNA called the promoter. This promoter region signals the start of a gene.
3. RNA Synthesis: RNA polymerase moves along the DNA template strand, reading the sequence of bases. As it does, it assembles a complementary RNA strand using free nucleotides.
* Base pairing rules: RNA uses uracil (U) instead of thymine (T). So, A in DNA pairs with U in RNA, while G in DNA pairs with C in RNA.
4. Termination: When RNA polymerase reaches a specific sequence on the DNA called the terminator, it stops transcription.
5. RNA Processing: The newly synthesized RNA molecule, called pre-mRNA, undergoes some modifications before it can leave the nucleus:
* Capping: A modified guanine nucleotide (5' cap) is added to the beginning of the pre-mRNA.
* Splicing: Non-coding regions called introns are removed, and the coding regions called exons are joined together.
* Polyadenylation: A tail of adenine nucleotides (poly-A tail) is added to the end of the pre-mRNA.
The final processed RNA molecule, called mRNA, is now ready to leave the nucleus and go to the ribosomes for protein synthesis (translation).
In summary, transcription is the process of converting DNA into RNA, and it involves unwinding DNA, binding RNA polymerase, synthesizing RNA, and processing the RNA molecule.
