Timeline of Molecular Biology Discoveries

Year	Scientist(s)	Discovery	Significance
1928	Frederick Griffith	Transformation in Streptococcus pneumoniae	Demonstrated heritable "transforming principle"
1944	Avery, MacLeod, McCarty	DNA identified as transforming principle	First proof DNA = genetic material
1950	Erwin Chargaff	A=T and G=C rules for dsDNA	Foundational for Watson-Crick model
1952	Alfred Hershey, Martha Chase	T2 phage infection with ^32P/^35S	Definitive proof DNA = genetic material
1952–53	Rosalind Franklin, Maurice Wilkins	X-ray crystallography of DNA (Photo 51)	Provided structural data for double helix
1953	James Watson, Francis Crick	Double helix structure of DNA	Nobel Prize 1962; central to all molecular biology
1958	Matthew Meselson, Franklin Stahl	Semiconservative replication via ^15N/^14N	Proved the mechanism of DNA replication
1958	Francis Crick	Central dogma of molecular biology	Framework: DNA→RNA→Protein
1961	François Jacob, Jacques Monod	Lac operon model of gene regulation	First model of regulated gene expression; Nobel 1965
1966	Marshall Nirenberg et al.	Complete cracking of the genetic code	All 64 codons assigned; Nobel 1968
1972	Paul Berg	First recombinant DNA molecule created	Foundation of genetic engineering
1984	Alec Jeffreys	DNA fingerprinting using VNTRs	Forensics, paternity testing revolution
1985	Kary Mullis	Polymerase Chain Reaction (PCR)	Nobel 1993; transformed molecular biology
1990–2003	Human Genome Project	Complete sequence of human genome	3.2 billion bp; ~20,000–25,000 genes