A mutation is a change in the genetic material of an organism. We are made from trillions of cells, each with a nucleus composed of DNA – a set of instructions that tells the cell what to do. Cells copy themselves with astonishing accuracy, but every now and then a piece of code is copied incorrectly. This is largely due to natural radiation bombarding us on a daily basis and interacting with our DNA. This incorrect piece of code can become a permanent change in the DNA – a mutation that can be copied further. Mutations are rarely harmful though. Indeed, most mutations go unnoticed, as the body has mechanisms to stop a cell copying itself when a mutation occurs. Sometimes mutations can even benefit organisms and promote diversity in a species. When a mutation allows an organism to cope better with an environmental stress, it will be passed on to future generations through natural selection.
Answered by Rik Sargent