DNA history

  • Watson and Crick discover the shape of DNA

    Watson and Crick discover the shape of DNA
    After James Watson and Francis Crick saw the DNA pictures taken by Rosalind Franklin, they tried several different models until they finally realized that DNA is in the form of a double helix with two strands of nucleotides.
  • Period: to

    1953 - 2004

  • 46 Chromosomes in Humans is Discovered

    46 Chromosomes in Humans is Discovered
    Joe Hin Tjio, a NIH (National Institution of Health) researcher, discovered the actual number of chromosomes in humans was 46. He published his findings sometime in April 1956.
  • DNA Polymerase

    DNA Polymerase
    Arthur Kornberg isolates DNA polymerase, an enzyme that will be used for many kinds of recombinant DNA techniques and sequencing. (year 1955, actual month and day not known)
  • Joe Hin Tjio Publishes findings on 46 Chromosomes

  • Semiconservative Replication of DNA

    Semiconservative Replication of DNA
    Matthew Meselson and Franklin Stahl discover that DNA replicates semiconservatively, each strand of DNA molecule from the parent generation pairing with a strand from the daughter generation. (actual date not known)
  • mRNA Function is Discovered

    mRNA Function is Discovered
    Sydney Brenner, Francois Jacob, and Matthew Meselson discover that mRNA is the molecule that delivers information from DNA to the ribosomes in the cytoplasm. (actual date not known)
  • Interpretation of Genetic Code

    Interpretation of Genetic Code
    After several years, Marshall Nirenberg, Har Khorana and Severo Ochoa had finally cracked the genetic code. Showing how nucleic acids (and their four-letter alphabet) determine the order of the twenty kinds of amino acids in proteins.
  • First Restriction Enzymes Described

    First Restriction Enzymes Described
    Several groups of researchers discovered that restriction enzymes recognize and cut specific short sequences of DNA. They’re found in bacteria, which use the enzymes to digest invading DNA. The enzymes became an important, early tool for mapping genomes. (actual date not known)
  • The First Recombinant DNA

    The First Recombinant DNA
    The first production of recombinant DNA molecules, using restriction enzymes. Recombinant DNA technology involves the joining of DNA from different species and subsequently inserting the hybrid DNA into a host cell, often a bacterium. (actual date not known)
  • First Animal Gene Cloned

    First Animal Gene Cloned
    Stanford and UCSF researchers fused a segment of DNA containing a gene from the African clawed frog (Xenopus) with DNA from the bacterium E. coli and placed the resulting DNA back into an E. coli cell. The frog DNA was copied and the gene it contained directed the production of a specific frog protein. It was the first animal gene to be cloned. (actual date not known)
  • DNA Sequencing

    DNA Sequencing
    Sanger developed a slightly different protocol for sequencing DNA. Sanger's method, where a marker attaches to the growing ends of DNA chains, is used most commonly in labs now. (Sanger is his name) (actual date not known) (actual years were from 1975 -77)
  • First Genetic Engineering Company

    First Genetic Engineering Company
    Herbert Boyer, one of the creators of recombinant DNA technology in the early 70s, founded Genentech with venture capitalist Robert Swanson. (actual date not known)
  • Discovery of Introns

    Discovery of Introns
    Richard Roberts' and Phil Sharp's labs showed that eukaryotic genes contain many interruptions, called introns. Human genes are on average interrupted about 10 times, and the introns typically contain about 90 percent of the DNA sequence in the whole gene. (actual date not known)
  • First Transgenic Animals

    First Transgenic Animals
    Scientists had been able to add new genes to bacterial cells for several years. In the early 80s, they figured out how to add stably-inherited new genes to animals. The first such "transgenic animals" were mice and fruit flies. (actual date not known)
  • First Genetic Disease Mapped

    First Genetic Disease Mapped
    A genetic marker linked to Huntingtons disease was found on chromosome 4 in 1983, making Huntingtons disease the first genetic disease mapped. (actual date not known)
  • Invention of PCR

    Invention of PCR
    PCR, the polymerase chain reaction, is a technique for amplifying DNA that greatly increased the pace of genetic research. In a few hours, PCR can make billions of copies of a specific segment of DNA. (actual date not known)
  • First Human Genetic Map

    The first comprehensive genetic map of human chromosomes was based on 400 restriction fragment length polymorphisms (RFLP). A genetic map contains landmarks, like RFLPs, that occur in various forms. Tracking which variants are inherited in different people can be used to locate genes responsible for diseases. (actual date not known)
  • The Human Genome Project Begins

    The Human Genome Project Begins
    The Human Genome Project begins in 1990, the objective was to find and map every gene in the human genome. (the day is not known)
  • ESTs

    An expressed-sequence tag (EST) is a stretch of DNA sequence made by copying a portion of an mRNA molecule. They were first proposed as a useful way to find genes in the genome in 1991. (actual date not known)
  • The Microbial Genome Program Begins

    The DOE began a Microbial Genome Program in late 1994 to sequence the genomes of some bacteria.
  • Physical Map of Human Genome Is Completed

    A physical map uses sequence-tagged sites (STSs) as markers to order large segments of DNA. One of the goals of the HGP was to complete a physical map with a marker every 100,000 base pairs by 1998. The map built by 1995 was a significant milestone toward that goal; it contained 15,086 STSs, spaced an average of 199,000 base pairs apart. (actual date not known)
  • Human Gene Map Created

    Scientists created a map showing the locations of ESTs representing fragments of more than 16,000 genes from throughout the genome. (actual date not known)
  • First Finished Sequence of a Human Chromosome

    First Finished Sequence of a Human Chromosome
    In 1999, the HGP completed the first finished, full-length sequence of a human chromosome, chromosome 22. This accomplishment demonstrated the power of the HGP method of clone-by-clone sequencing to obtain large amounts of highly accurate sequence. (actual date not known)
  • First Draft of the Human Genome Sequence

    First Draft of the Human Genome Sequence
    The Human Genome Project international consortium published a first draft of the human genome sequence. The draft sequence covered more than 90 percent of the human genome. (actual date not known)
  • The Completion of the Human Genome Project

    The Completion of the Human Genome Project
    The International Human Genome Sequencing Consortium announced the successful completion of the Human Genome Project more than two years ahead of schedule and under budget. (actual date not known)