Our quest to understand how our genes work started in earnest in the mid-19th Century when a biologist and monk called Gregor Mendel came to a startling conclusion about the traits of plants. He crossed purple flowered pea plants with white ones, and found that all the resulting offspring were purple. However, he noticed that the third generation produced both colours.

This revealed that a characteristic such as colour can be inherited, with one trait more dominant than another. In a way, Mendel had figured out what genes did, but not what they were, or even looked like.

This came much later. It was only in the following century that the very structure of DNA was discovered. Building on the work of Rosalind Franklin and Maurice Wilkins, in 1953 James Watson and Francis Crick discovered that our DNA is formed in a double helix.

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