The event is called mutation
A mutation is a rare, accidental or induced modification of genetic information in the genome, specifically DNA.Depending on which part of the genome is affected, the consequences of a mutation may vary.
A mutation is said to be hereditary if the mutated genetic sequence is transmitted to the next generation (see germinal mutations).
It is one of the elements of biodiversity and one of the many factors that may be involved in the evolution of the species (for example: production of new protein which help the bacteria to grow in hostile environment like fungi).
