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DNA unzips to reveal the base sequence on the coding strand.

RNA moves in and aligns itself with the base pairs in the complementary sequence (A+U C+G) U replaces thymine.

DNA is read from the 3' to the 5' and mRNA is assembled from the 5' to 3'.

Only the exons (the coding parts of DNA) are copied into the mRNA.

The completed mRNA molecule detaches from the DNA and exits the nucleus via a nuclear pore.

Transciption

TRANSLATION - organised by the ribosomes.

Ribosomes attach themselves to the mRNA (magnesim ions are involved here). Each ribosome controls the making of one polypeptide

mRNA is read as a triplet of bases called codons.

Ribosomes are made of two subunits, the smaller attaches to the mRNA. The larger subunit attaches to the two other codons, one is P and one an A.

An anticodon is attracted, the anticodon is part of the transfer RNA (tRNA). The codon and anticodon bond with hydrogen bonds. Each anticodon has a amino acid with it.

These hydrogen bonds cause two amino acids to be held together long enough for a peptide bond to be formed.

The first (or start codon) is AUG, this catalyses peptidyl transferase.

once the first peptide bond has formed the first tRNA detaches and travels to another amino acid.

Translation.

The ribosome shifts along the RNA by one codon, starting the whole process again.