DNA (iStock)DNA, or deoxyribonucleic acid, is more than just a macromolecule; it is set of instructions for building living cells. Bundles of DNA, called chromosomes, decide our genetic makeup; whether we have brown eyes or black hair. Watson and Crick discovered the double helix structure of DNA in 1953 (using Rosalind Franklin's crystallographic data). 50 years later, in 2003, the Human Genome Project was completed. Today DNA sequencing can work out the order of all the nucleotides in a set of your chromosomes for less than £1000.

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