2. The sequence of bases in a section of DNA determines the sequence of amino acids in the protein it codes for.

3. These are the four bases found in DNA: adenine, guanine, thymine and cytosine.

4. These are transcribed into messenger RNA (mRNA) in the nucleus.

6. Guanine in mRNA is complementary to cytosine in DNA.

7. Adenine in mRNA is complementary to thymine in DNA.

8. Cytosine in mRNA is complementary to guanine in DNA.

9. mRNA does not contain thymine. Uracil in mRNA is complementary to adenine in DNA.

10. Let’s look at a section of DNA and the complementary mRNA.

11. Remember that in mRNA uracil is complementary to adenine.

13. See if you can predict the complementary bases.

25. Genetic information is encoded as a triplet code. Each set of three bases in mRNA is a codon.

26. Genetic information is encoded as a triplet code. Each set of three bases in mRNA is a codon.

27. Genetic information is encoded as a triplet code. Each set of three bases in mRNA is a codon.

28. Genetic information is encoded as a triplet code. Each set of three bases in mRNA is a codon.

29. Genetic information is encoded as a triplet code. Each set of three bases in mRNA is a codon.

30. mRNA can leave the nucleus, carrying the code for protein synthesis.

32. The code carried by mRNA is translated with the aid of transfer RNA (tRNA) and particles in the cell called ribosomes.

33. Each different tRNA molecule carries an anti-codon, which is complementary to a triplet of bases on mRNA.

34. Different tRNA molecules are able to recognise different amino acids and attach to them.

35. Here, a tRNA molecule carrying the anti-codon GAC joins to a leucine molecule (Leu).

36. tRNA molecules can carry amino acids towards mRNA molecules.

37. Specific anti-codons on tRNA recognise and bind to codons on mRNA.

38. In this example, four different tRNA molecules carry amino acids towards the mRNA molecule.

39. In this example, four different tRNA molecules carry amino acids towards the mRNA molecule.

40. In this example, four different tRNA molecules carry amino acids towards the mRNA molecule.

41. In this example, four different tRNA molecules carry amino acids towards the mRNA molecule.

42. The tRNA molecules bind to the mRNA molecule in the ribosome and a bond forms between the two amino acids that they carry.

43. Having delivered its amino acid, the tRNA molecules separates from the mRNA and leaves the ribosome. The ribosome moves further along the mRNA chain.

44. Having delivered its amino acid, the tRNA molecules separates from the mRNA and leaves the ribosome. The ribosome moves further along the mRNA chain.

45. Having delivered its amino acid, the tRNA molecules separates from the mRNA and leaves the ribosome. The ribosome moves further along the mRNA chain.

46. Having delivered its amino acid, the tRNA molecules separates from the mRNA and leaves the ribosome. The ribosome moves further along the mRNA chain.

47. A bond forms between the next two amino acids.

48. The process continues.

55. Eventually a complete protein is synthesised. Certain mRNA codons (UAA, UGA and UAG) code for a stop, signalling the release of the completed protein.

56. Eventually a complete protein is synthesised. Certain mRNA codons (UAA, UGA and UAG) code for a stop, signalling the release of the completed protein.

57. Eventually a complete protein is synthesised. Certain mRNA codons (UAA, UGA and UAG) code for a stop, signalling the release of the completed protein.

58. The triplet base codes (codons) for mRNA with the corresponding amino acids.