In sperm/egg cells and is therefore heritable. All the cells of the offspring contain the mutation, but the phenotype is only expressed in genes/cells that usually express that gene. Not heritable, only affects somatic cells arising from the original cell so if one cell is mutated in the 2 cell stage, half the organisms cells will be affected e. g. cancer. Can occur at every dna synthesis stage of cell division e. g. hu(cid:374)ti(cid:374)gto(cid:374)"s, acho(cid:374)droplasia (cid:894)dwarfis(cid:373)(cid:895) autosomal dominant, haemophilia, duchenne. Caused by environmental mutagens (a mutagen is anything that binds to dna increases mutation rate) Chromosomal mutations can involve many genes and be visible at the light microscope level: deletion, duplication, inversion, translocation e. g. chronic myelogenous leukaemia (cml) Brings together two genes that would usually be separate. Small a small number of dna bases. Silent (no change in gene product): degeneracy and wobble. Missense (amino acid substitution in gene product) can be first, second or third base.