What is the meaning of the mutation rate in genetic algorithms? Let us suppose that we have a mutation rate of 5%. What does this mean?


Each gene of each individual has 5% of probability of change to another value? At the end, around 5% of the genes of each individual in the population will be changed.
Each individual in the population has 5% of probability of having a random gene changed to antoher value? At the end, 5% of the population will have a change in some of its genes.


Besides that...Should I apply the mutation operator over all individuals or only to the children generated by the crossover operator?
In general each child is mutated separately, only once at 'birth', and not during their 'adulthood'. Depending on how individuals are specified, '5% mutation' might mean that a random 5% of the bits in the individual's source code are flipped.