A vaccine is a substance that supports the body to produce antibodies and offer immunity in contradiction of a disease. A live attenuated vaccine comprises a version of the living microbe that has been destabilized because they are still alive this is the closest thing to an actual infection and will habitually lead the body to have a lifelong immunity after only one or two doses. A killed vaccine is created by killing the illness with chemicals, heat or radiation in which these vaccines are harmless but rouse a weaker immune reaction.
Yes, crossing over does not occur during mitosis. As mitosis is simply the duplication of cells, there is no gene variation that comes from crossing-over.
