Science in Context: A Comparative Timeline

1950

E. Chargaff lays the foundations for nucleic acid structural studies by his analytical work. He demonstrates for DNA that the numbers of adenine and thymine groups are always equal and so are the numbers of guanine and cytosine groups. These findings later suggest to Watson and Crick that DNA consists of two polynucleotide strands joined by hydrogen bonding between A and T and between G and C.
E. M. Lederberg discovers lambda, the first viral episome of E. coli.

1950

1951

N. D. Zinder and J. Lederberg describe transduction in Salmonella.
J. Lederberg and E. M. Lederberg invent the replica plating technique.
F. Sanger and his colleagues work out the complete amino acid sequence for the protein hormone insulin, and show that it contains two polypeptide chains held together by disulfide bridges.
A. D. Hershey and M. Chase demonstrate that the DNA of phage enters the host, whereas most of the protein remains behind.

1952

J. D. Watson and F. H. C. Crick propose a model for DNA comprised of two helically intertwined chains tied together by hydrogen bonds between the purines and pyrimidines.
W. Hayes discovers polarized behavior in bacterial recombinations. He isolates the Hfr H strain of E. coli and shows that certain genes are readily transferred from Hfr to F- bacteria, whereas others are not.

1953 Dwight D. Eisnehower becomes thirty-fourth president of the United States.

1954

S. Benzer works out the fine structure of the rII region of phage T4 of E. coli, and coins the terms CISTRON,RECON, and MUTON.
1955

F. Jacob and E. L. Wollman are able experimentally to interrupt the mating process in E. coli and show that a piece of DNA is inserted from the donor bacterium into the recipient.
1956

V. M. Ingram reports that normal and sickle-cell hemoglobin differ by a single amino acid substitution.
1957

F. Jacob and E. L. Wollman demonstrate that the single linkage group of E. coli is circular and suggest that the different linkage groups found in different Hfr strains result from the insertion at different points of a factor in the circular linkage group that determines the rupture of the circle.
F. H. C. Crick suggests that during protein formation the amino acid is carried to the template by an adaptor molecule containing nucleotides and that the adaptor is the part that actually fits on the RNA template. Crick thus predicts the discovery of transfer RNA.
M. Meselson and F. W. Stahl use the density gradient equilibrium centrifugation technique to demonstrate the semiconservative distribution of density label during DNA replication in E. coli.
George W. Beadle, Edward L. Tatum, and Joshua Lederberg share a Nobel Prize in Medicine for Beadle and Tatum's discovery that genes act by regulating definite chemical events, and for Lederberg's discoveries concerning genetic recombination and the organization of the genetic material of bacteria.
Frederick Sanger receives a a Nobel Prize in Chemistry for his work on the structure of proteins, especially that of insulin.

1958

J. Lejeune, M. Gautier, and R. Turpin show that Down syndrome is a chromosomal aberration involving trisomy of a small telocentric chromosome.
R. L. Sinsheimer demonstrates that bacteriophage phiX174 of E. coli contains a single-stranded DNA molecule.
Severo Ochoa and Arthur Kornberg share a Nobel Prize in Medicine for their discovery of the mechanisms in the biological synthesis of ribonucleic acid and deoxiribonucleic acid.

1959

1960


	1950
E. Chargaff lays the foundations for nucleic acid structural studies by his analytical work. He demonstrates for DNA that the numbers of adenine and thymine groups are always equal and so are the numbers of guanine and cytosine groups. These findings later suggest to Watson and Crick that DNA consists of two polynucleotide strands joined by hydrogen bonding between A and T and between G and C. E. M. Lederberg discovers lambda, the first viral episome of E. coli.	1950
	1951
N. D. Zinder and J. Lederberg describe transduction in Salmonella. J. Lederberg and E. M. Lederberg invent the replica plating technique. F. Sanger and his colleagues work out the complete amino acid sequence for the protein hormone insulin, and show that it contains two polypeptide chains held together by disulfide bridges. A. D. Hershey and M. Chase demonstrate that the DNA of phage enters the host, whereas most of the protein remains behind.	1952
J. D. Watson and F. H. C. Crick propose a model for DNA comprised of two helically intertwined chains tied together by hydrogen bonds between the purines and pyrimidines. W. Hayes discovers polarized behavior in bacterial recombinations. He isolates the Hfr H strain of E. coli and shows that certain genes are readily transferred from Hfr to F- bacteria, whereas others are not.	1953	Dwight D. Eisnehower becomes thirty-fourth president of the United States.
	1954
S. Benzer works out the fine structure of the rII region of phage T4 of E. coli, and coins the terms CISTRON,RECON, and MUTON.	1955
F. Jacob and E. L. Wollman are able experimentally to interrupt the mating process in E. coli and show that a piece of DNA is inserted from the donor bacterium into the recipient.	1956
V. M. Ingram reports that normal and sickle-cell hemoglobin differ by a single amino acid substitution.	1957
F. Jacob and E. L. Wollman demonstrate that the single linkage group of E. coli is circular and suggest that the different linkage groups found in different Hfr strains result from the insertion at different points of a factor in the circular linkage group that determines the rupture of the circle. F. H. C. Crick suggests that during protein formation the amino acid is carried to the template by an adaptor molecule containing nucleotides and that the adaptor is the part that actually fits on the RNA template. Crick thus predicts the discovery of transfer RNA. M. Meselson and F. W. Stahl use the density gradient equilibrium centrifugation technique to demonstrate the semiconservative distribution of density label during DNA replication in E. coli. George W. Beadle, Edward L. Tatum, and Joshua Lederberg share a Nobel Prize in Medicine for Beadle and Tatum's discovery that genes act by regulating definite chemical events, and for Lederberg's discoveries concerning genetic recombination and the organization of the genetic material of bacteria. Frederick Sanger receives a a Nobel Prize in Chemistry for his work on the structure of proteins, especially that of insulin.	1958
J. Lejeune, M. Gautier, and R. Turpin show that Down syndrome is a chromosomal aberration involving trisomy of a small telocentric chromosome. R. L. Sinsheimer demonstrates that bacteriophage phiX174 of E. coli contains a single-stranded DNA molecule. Severo Ochoa and Arthur Kornberg share a Nobel Prize in Medicine for their discovery of the mechanisms in the biological synthesis of ribonucleic acid and deoxiribonucleic acid.	1959
	1960