1. Initiation:
- RNA polymerase, an enzyme, binds to a specific region on the DNA called the promoter.
- The promoter sequence signals the start of a gene.
- The DNA double helix unwinds, exposing the template strand that will be used to synthesize the RNA.
2. Elongation:
- RNA polymerase moves along the template strand of the DNA.
- As it moves, it reads the DNA sequence and uses it to build a complementary RNA molecule.
- The RNA nucleotides are added one by one to the growing RNA chain, following the base pairing rules:
- Adenine (A) pairs with Uracil (U)
- Thymine (T) pairs with Adenine (A)
- Guanine (G) pairs with Cytosine (C)
- The newly synthesized RNA strand grows in the 5' to 3' direction.
3. Termination:
- RNA polymerase reaches a specific sequence on the DNA called the terminator.
- This sequence signals the end of the gene.
- RNA polymerase detaches from the DNA, and the newly synthesized RNA molecule is released.
Key points to remember:
- Only one strand of DNA is used as the template for transcription.
- The RNA molecule produced is a copy of the DNA sequence, but with uracil (U) replacing thymine (T).
- Transcription occurs in the nucleus of eukaryotic cells.
Types of RNA:
- Messenger RNA (mRNA): Carries genetic information from DNA to ribosomes for protein synthesis.
- Transfer RNA (tRNA): Transports amino acids to ribosomes during protein synthesis.
- Ribosomal RNA (rRNA): Forms part of the ribosomes, the cellular machinery that synthesizes proteins.
