Mutations occur when segments of DNA are accidentally rearranged through the deletion, insertion, or substitution of one or more nucleotides. The diagram below shows how a nucleotide sequence can be changed by these mutations. If one or more of these mutations occurs in the genes of reproductive cells, how might the traits of offspring be affected?

If a mutation occurs in the genes of reproductive cells (gametes) that mutation is termed a germinal mutation. Germinal mutations usually are not expressed in the individual containing the mutation, but gametes that carry the mutation will pass it on to the offspring. So, we say that the germinal mutations are hereditary mutations, inherited from a parent and present in every somatic and germline cell in the offspring.