1. Protein Synthesis  Human life is impossible without proteins. Why? Proteins are of two Kinds 1. Structural 2. Functional Actin & Myosin: muscle proteins Keratin: nails, hair, horns, feathers Collagen: bones, teeth, cartilage, tendons, ligament, blood vessels, skin matrix Enzymes Antibodies Haemoglobin

2. Protein Synthesis takes place on two major steps: 1. Transcription 2. Translation

4. Transcription:  Takes place inside the nucleus  DNA unzips (one gene) and a complimentary copy of this gene called mRNA (messenger RNA) is formed from RNA nucleotides  The newly formed mRNA leaves the nucleus through the a nuclear pore

5. Translation:  Takes place in the cytoplasm  The freely floating ribosomes or the ones sticking to the RER start reading the message on the mRNA  Reading the message takes place three nitrogenous bases at a time (triplets), each triplet is called a codon  tRNA (transfer RNA) which is found in the cytoplasm has the appropriate anti-codon for each codon which is equivelant to one specific amino acid  There are 20 different amino acids that enter in the synthesis of polypeptides (proteins)

6. Translation:

8. Mutations 1. Chromosomal mutations 2. Gene mutations All or part of a chromosome. e.g.: Down's Syndrome * Any of such mistakes results in a wrong protein being synthesized. Deletion: deletion of one nitrogenous base Addition: adition of one nitrogenous base Substitution: one nitrogenous base is replaced by another