Figure 7. The Nobel Stamps of 1989. The stamps of eight geneticists and Nobel Laureates (Physiology or Medicine) were engraved by Martin Mörck after originals by Göran Österlund. And printed by recess/offset at the PFA. The FDC illustration is by Göran Österlund and the postmark is by Jan Magnusson; copyrighted 1989, Sweden Postal Stamps. The discoveries presented are using fruit flies Thomas H. Morgan showed how the genes are linked in the chromosomes (1933); James. D. Watson and F.H.C. Crick solved the riddle of the molecular structure of DNA with the aid of M.H.F. Wilkins diffractogram. The DNA molecule contains the genetic material storing hereditary information (1962); Werner Arber, Daniel Nathans and Hamilton D. Smith (1978) discovered the enzymes with which it is possible to cut a DNA molecule in predetermined places. If DNA molecules are cut from different animal species, the ends can be joined together to form hybrid DNA molecules; Barbara McClintock (1983) discovered how genes sometimes change places on the chromosomes, the so called "jumping genes".