A mutation is a change in the DNA sequence of an organism. This change can happen naturally during cell division or can be caused by environmental factors like radiation or chemicals. Mutations can affect how an organism looks, behaves, or functions, and they can be passed down to future generations if they occur in reproductive cells. Some mutations are harmless, while others can lead to diseases or other health issues. For example, a mutation in the BRCA1 gene can increase the risk of breast cancer. On the other hand, some mutations can be beneficial, helping organisms adapt to their environment, like the peppered moth changing color during the Industrial Revolution.