Any relatively stable heritable change in genetic material that may be a chemical transformation of an individual gene ( gene or point mutation), altering its function, or a rearrangement, gain or loss of part of a chromosome, that may be microscopically visible (chromosomal mutation); mutation can be either germinal and inherited by subsequent generations, or somatic and passed through cell lineage by cell division. Related term: chromosome, gene. Related term: clastogenesis, genotoxicity