1865 Genes are particulate factors 1871 Discovery of nucleic acids 1.1 1903 Chromosomes are hereditary units Introduction 1910 Genes lie on chromosomes 1913 Chromosomes contain linear arrays of genes 1927 Mutat ions are phy sical changes in genes 1931 Recombinat ion is caused by crossing over 1944 DNA is the genetic mat erial 1945 A gene codes for protein 1951 First protein sequence 1953 DNA is a double helix 958 DNA replicates semiconseratively 1961 Genetic code is triplet Figure lI A briet 1977 Eukaryotic genes are interrupted history of genetics 1977 DNA can be sequenced 1995 First genome sequenced 消当Figure 1.1 A brief history of genetics. 1.1 Introduction