In 1953 the double helix was discovered a twisted-ladder structure of  DNA.this discovery was made by  James Watson ,Francis Crick,and maurice wilkins. This changed the history of science and gave rise to modern  biology, which helps us understanding how genes control the chemical processes within cells. Before this scientis knew the word gene meant the smallest unit of genetic information but they did not know what a gene actually looked like and how it was copied, with very few errors, generation after generation.The same year a biochemist Erwin Chargaff had found the four types DNA  A and G, and C and T .