|
1957
|
|
Francis Crick and George Gamov
worked out the "central dogma," explaining how DNA functions to
make protein. Their "sequence hypothesis" posited that the DNA sequence
specifies the amino acid sequence in a protein. They also suggested
that genetic information flows only in one direction, from DNA to
messenger RNA to protein, the central concept of the central dogma.
Matthew Meselson and Frank Stahl
demonstrated the replication mechanism of DNA.
|
| 1958 |
|
Coenberg
discovered and isolated DNA polymerase, which became the first enzyme
used to make DNA in a test tube. |
| 1959 |
|
Francois Jacob and Jacques Monod established the existence of genetic
regulation - mappable control functions located on the chromosome
in the DNA sequence - which they named the repressor and operon. They
also demonstrated the existence of proteins that have dual specificities.
|
| 1961 |
|
Marshall
Nirenberg built a strand of mRNA comprised only of the base uracil.
This strand is called "poly-u," and by examining it Nirenberg discovered
that UUU is the codon for phenylalanine. This was the first step in
cracking the genetic code, which Nirenberg and colleagues succeeded
in doing within five years. |
| 1966 |
|
The genetic
code was "cracked". Marshall Nirenberg, Heinrich Mathaei, and Severo
Ochoa demonstrated that a sequence of three nucleotide bases (a codon)
determines each of 20 amino acids. |
| 1967 |
|
Mary Weiss
and Howard Green took a crucial step in human gene mapping with the
publication of a technique for using human cells and mouse cells grown
together in one culture. This was called somatic-cell hybridization.
|
| 1969 |
|
Leonard
Herzenberg, a geneticist at Stanford, developed the fluorescence-activated
cell sorter, which can identify up to 5,000 closely related animal
cells. |
| 1970 |
|
Howard Temin and David Baltimore,
working independently, first isolated "reverse transcriptase" a
restriction enzyme that cuts DNA molecules at specific sites. Their
work described how viral RNA that infects a host bacteria uses this
enzyme to integrate its message into the host's DNA. This discovery
allowed scientists to create clones and observe their function.
|
| 1972 |
|
Immunologist Hugh McDevitt, in
an article in Science, reported observing genes that control immune
responses to foreign substances. His observations suggested predictable,
inherited susceptibility to some diseases.
The first successful DNA cloning
experiments were performed in California.
|
| 1973 |
|
Scientists for the first time successfully
transferred deoxyribonucleic acid (DNA) from one life form into
another.
Stanley Cohen and Annie Chang of
Stanford University and Herbert Boyer of UCSF "spliced" sections
of viral DNA and bacterial DNA with the same restriction enzyme,
creating a plasmid with dual antibiotic resistance. They then spliced
this recombinant DNA molecule into the DNA of a bacteria, thereby producing the first
recombinant DNA organism. Bruce Ames, a biochemist at UC Berkeley,
developed a test to identify chemicals that damage DNA. The Ames
Test becomes a widely used method to identify carcinogenic substances.
|
