The genetic variations exist due to reshuffling of genes caused by recombinations or by mutations. The recombinations are produced by the routine reshuffling of genes during independent assortment of chromosomes, reciprocal crossing of genes during crossing over and random fertilization of gametes. Mutation is the sudden inheritable discontinuous variation which appears in an organism due to permanent changes in its genotype. Mutation can occur at any stage during the development. Mutations are heritable changes, that is, if they appear in somatic cells they are inherited to daughter cells by mitosis but if they appear in gamete cells they are inherited to the offsprings. The former are known as somatic mutations and latter as germ mutations. They bring about a change in the genetic message and cause variation