- There are 20 different amino acids in human proteins. A cell uses the sequence of bases in DNA to synthesise chains of these amino acids. These chains form proteins and this process is called protein synthesis.
- Each amino acid is identified by a different group of bases. A specific order of bases in DNA produces a specific order of amino acids in the chain and therefore produces a particular protein.
- The first process of making a protein is called transcription. This takes place in the nucleus.
- The DNA in a gene unzips by breaking the weak hydrogen bonds holding the bases together in the double helix.
- mRNA (messenger) nucleotide in nucleus
- mRNA nucleotides bind with complementary bases on the coding strand NB: Thymine becomes Uracil in RNA
- mRNA strand leaves nucleus through nuclear pores by detaching from the coding strand
- DNA zips up
- mRNA attaches to a ribosome in the cytoplasm.
- Ribosome decodes the mRNA
- tRNA (transfer) codons are attached to amino acids, each codon has a different amino acid
- tRNA codons join to the complementary codons (bases) on the mRNA
- As more amino acids are brought by the tRNA they bond together with peptide bonds.
- Long chain of amino acids forms a polypeptide
- Protein formed.