The gene is the basic unit of genetic material that is transmitted from father and mother to offspring . Many disease is transmitted from one generation to other because of gene mutation .Gene mutation is the "heritable alteration or change in genetic material". The gene mutation has four types each is different a dangerous. Deletion, substitution ,insertion and point mutation are the types of gene mutation. This report will cover the three types :substitution, insertion and deletion except point mutation because it is not common.