1. DNA fails to accurately copy
Most of the mutations naturally occur. When a cell divides, it makes a copy of its DNA — and sometimes the copy is not quite perfect, thus making a mutation.
2. Environmental influences
Mutations can occur when you have been exposed to chemical radiation etc. because when DNA is damaged when coming into contact with dangerous substances it tries to repair itself, but doesn't always do a good job- thus creating a mutation.
- I don't know a third sorry -
