Molecular Biology History Timeline

Friedrich Miescher discovers “nuclein”,1869,CE,Miescher isolates a phosphorus‐rich substance from the nuclei of pus cells later identified as DNA laying foundation for molecular genetics,molecular biology

Oswald Avery, Colin MacLeod, and Maclyn McCarty demonstrate DNA is genetic material,1944,CE,Avery and colleagues show that purified DNA from Streptococcus pneumoniae can transform nonvirulent bacteria into virulent form proving DNA carries hereditary information,molecular biology

Erwin Chargaff formulates Chargaff’s rules,1950,CE,Chargaff reports that in DNA the amount of adenine equals thymine and cytosine equals guanine establishing base‐pairing stoichiometry crucial for understanding DNA structure,molecular biology

James Watson and Francis Crick propose double helix structure of DNA,1953,CE,Watson and Crick integrate Rosalind Franklin’s X‐ray diffraction data with biochemical evidence to model DNA as two antiparallel strands with complementary base pairing explaining replication and information transfer,molecular biology

Matthew Meselson and Franklin Stahl confirm semiconservative DNA replication,1958,CE,Meselson and Stahl use isotope‐labeling and density‐gradient centrifugation to demonstrate that each daughter DNA molecule contains one parental and one newly synthesized strand providing direct evidence for Watson‐Crick replication mechanism,molecular biology

George Beadle and Edward Tatum establish “one gene–one enzyme” hypothesis,1958,CE,Beadle and Tatum’s experiments with Neurospora crassa show mutations in single genes disrupt specific enzymatic steps linking genes directly to proteins and laying groundwork for biochemical genetics,molecular biology

Marshall Nirenberg and J. Heinrich Matthaei decipher first codon,1961,CE,Nirenberg and Matthaei synthesize polyuracil RNA templates in vitro showing UUU codes for phenylalanine initiating elucidation of the genetic code and mRNA translation,molecular biology

François Jacob and Jacques Monod propose operon model for gene regulation,1961,CE,Jacob and Monod describe the lac operon in Escherichia coli identifying promoter, operator, and repressor elements demonstrating how gene expression is regulated at transcriptional level,molecular biology

Walter Gilbert and Allan Maxam develop DNA sequencing methods,1977,CE,Gilbert develops chemical cleavage sequencing while Maxam and Gilbert introduce a base‐specific chemical method enabling determination of nucleotide sequences and facilitating subsequent genome studies,molecular biology

Frederick Sanger introduces dideoxy chain‐termination DNA sequencing,1977,CE,Sanger’s method uses labeled dideoxynucleotides to terminate DNA synthesis at specific bases allowing rapid and accurate determination of nucleotide sequences and becomes the gold standard for decades,molecular biology

Herbert Boyer and Stanley Cohen create first recombinant DNA molecules,1973,CE,Boyer and Cohen splice foreign DNA into E. coli plasmids using restriction enzymes and DNA ligase demonstrating gene cloning and establishing foundations for genetic engineering,biotechnology

Kary Mullis invents polymerase chain reaction (PCR),1983,CE,Mullis designs a method using thermostable Taq DNA polymerase to amplify specific DNA fragments exponentially in vitro revolutionizing molecular diagnostics, forensics, and research,molecular technique

Edwin Southern publishes Southern blotting technique,1975,CE,Southern develops a method to transfer DNA fragments from gel to membrane and probe for specific sequences enabling detection of gene presence and copy number in genomic DNA,molecular biology

Brian Druker develops first tyrosine kinase inhibitor for chronic myeloid leukemia,2001,CE,Druker’s work on Gleevec (imatinib) targets BCR‐ABL fusion protein in leukemia cells demonstrating molecularly targeted therapy based on oncogene understanding,molecular medicine

International Human Genome Project completion,2003,CE,International consortium announces near‐complete reference sequence of human genome identifying ~20 000–25 000 protein–coding genes and providing a resource for functional genomics and personalized medicine,genomics

Jennifer Doudna and Emmanuelle Charpentier develop CRISPR‐Cas9 gene editing system,2012,CE,Doudna and Charpentier engineer RNA‐guided Cas9 nuclease to introduce precise, programmable DNA double‐strand breaks in living cells enabling targeted genome editing across species,molecular biology

Rosalind Franklin’s X‐ray diffraction images publicly recognized for DNA structure,2020,CE,Archival release and analysis of Franklin’s original Photo 51 data underscore her critical contributions to elucidating DNA double helix validating her role in molecular biology history,molecular biology