4.1 What is a gene?

On planet Earth there was a living being, and in the living being there was a cell, and in the cell there was a nucleus, and in the nucleus there were chromosomes, and the chromosomes were made up of DNA, and DNA was made up of an alphabet that produced life …

A gene is a section of DNA made up of sequences of the four nucleotide monomers adenine (A), thymine (T), cytosine (C) and guanine (G). It is the instruction to make a single product, such as a protein. Genes might seem like they are a jumble of monomers, but amazingly just those four ‘letters’ – A, T, C and G – encode all living things in DNA. This same short alphabet in combination is used by you (a human), the mosquito biting your leg, the bacteria on the mosquito’s leg and the virus inside the mosquito. And can you believe that the tiny mosquito has almost as many genes as you do?