1. The RNA polymerase attaches to the DNA double helix at the beginning of a gene.
2. The hydrogen bonds break between the two DNA strands in the gene break, seperating the strands and the DNA molecule uncoils at that point. One of the strands is then used as a template to make an mRNA copy.
4. The RNA polymerase lines up free RNA nucleotides alongside the template strand. Complimentary base pairing means that the mRNA strand ends up being a complimentary copy of the DNA template strand (except T is replaced by U in RNA).
5.Once the RNA nucleotides have paired up with their specific bases in the DNA strand they're joined together forming an mRNA molecule.
6. The RNA polymerase moves along the DNA seperating the strands and assembling the mRNA strand.
7. The hydrogen bonds between the uncoiled strands of DNA re-form once the RNA polymerase has passed by and the strands coil back into a double-helix.
8. When RNA polymerase reaches a stop codon, it stops making mRNA and detaches from the DNA.
9. The mRNA moves out of the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm where Translation occurs
Translation happens at the ribosomes in the cytoplasm. Amino acids are joined together to make a polypepetide chain following the sequence of codons carried by the mRNA.
1. The mRNA attaches to a ribosome and tRNA molecules carry amino acids to the ribosome.
2. A tRNA molecule with an anticodon that's complimentary to the start codon on the mRNA attaches itself to the mRNA by complimentary bas pairing.
3. A second tRNA molecule attaches itself to the next codon on the mRNA in the same way.
4. rRNA in the ribosome catalyses the formation of a peptide bond between the two amino acids attached to the the tRNA molecules. This joins the amino acids together. The first tRNA molecule moves away leaving its amino acid behind.
5. A third tRNA molecule binds to the next codon on the mRNA. Its amino acid binds to the first two and the second tRNA molecule moves away.
6.This process continues, producing a chain of linked amino acids until theres a stop codon on the mRNA molecule.
7. The polypeptide chain moves away from the ribosome and translation is complete.