Francis, what is the human genome?
The human genome is the entire collection of the DNA of our species. Human DNA carries information by a series of chemical bases. This information has only four letters in its alphabet: A, C, G and T. In the double helix of DNA, these letters appear like rungs on a ladder in four possible pairs: A-T, T-A, C-G and G-C. Because they combine only in this way, if you split all the pairs in half, cutting the ladder down the centre of each rung, each half-ladder contains all the information needed to rebuild a complete copy of the original. DNA is a bit like a software program that sits in the nucleus of a cell. A particular instruction – a gene – comprises hundreds of thousands of letters of ACGT code. The whole of the human genome is 3.1 billion of those letters. Such is the complexity of the information carried within each of the one hundred trillion cells of the human body, that if someone read the code out loud at three letters per second, it would take 31 years to complete. The human g
