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Friedrich Miescher
Miescher experimented on and discovered "nuclein" along with associated proteins from nuclei. He concluded they were constructed of hydrogen, oxygen, nitrogen, and phosphorous. -
Frederick Griffith
Griffith experimented with (r) rough and (s) smooth bacterium using mice. The S strain killed the mice while the R strain did not but the heat killed S-strain bacteria mixed with live R-strain bacteria did kill the mice. He concluded that something in the killed S strain was "transforming" the bacteria from one strain into another strain. -
Oswald Avery, Maclyn McCarty, & Colin Macleod
The trio’s discoveries came from studying Streptococcus pneumoniae, bacteria that can cause pneumonia. They continued to experiment with the R and S bacterium to figure out why they react the way they do, especially after being mixed together. They were able to rule out proteins as genetic material and determine that DNA is the substance that controls the characteristics of organisms. -
Erwin Chargraff
Chargraff worked with the chemistry of nucleic acids. The first step of his experiment was the separation of the DNA mixture into individual components by paper chromatography. Next, the separated compounds were converted into mercury salts. And finally, the purines and pyrimidines were identified via their ultraviolet absorption spectra. He eventually perfected his experiment and proved that adenine units equals the number of thymine units and guanine equals the number of cytosine units. -
Rosalind Franklin & Maurice Wilkins
Franklin and Wilkins determined that DNA consists of two chains twisted around each other or double helixes. Other discoveries and experiments helped support their discovery like how it was proven DNA is genetic material and not protiens. -
Alfred Hersey and Martha Chase
Hershey and Chase worked together experimenting with viruses and bacteria. They concluded viruses are not made of cells, they are basically DNA inside a protein coat. They used different radioactive elements to label the DNA and proteins in viruses. This allowed them to identify which molecule the viruses inserted into bacteria. They identified DNA as the molecule and concluded DNA is genetic material. -
James Watson & Frances Crick
This duo discovered the double helix DNA structure. This structure included a spiral of 2 DNA strands that each contain a long chain of monomer nucleotides.They proved another scientist's theory of DNA structure wrong, and the double helix was widely accepted soon after Watson & Crick discovered it. -
Barbara McClintock
Mc Clintock discovered the telomere and centromere locations and functions in the cell. Also, while studying maize (corn), she discovered Transposons. Transposons are DNA sequences that can change their location on the genome; they are nicknamed "jumping genes" because of this. They are found in almost all organisms. -
Linus Pauling
It started when Pauling returned from England and joined a Caltech biology seminar given by Robley Williams. Using Williams photos and x-ray patterns, Pauling was able to conclude that DNA was a three-stranded structure with the phosphates on the inside, a triple helix. -
Matthew Meselson & Franklin Stahl
This pair created an experiment later entitled, "Th Meselson-Stahl Experiment." It verified Watson and Crick's theory that DNA was structured in a double helix and explained how DNA is replicated. Beginning in October of 1975, they grew E. Coli and studied the replication of its DNA. They concluded that after replication, there is one new daughter subunit and 1 subunit for the parental DNA. -
Paul Berg
Berg conducted a gene-splicing experiment. During this, he spliced the DNA of the virus lambda into the DNA of another virus, SV40. This looped the DNA of both viruses together, as shown in the diagram. It created recombinant DNA. -
Frederick Sanger
Sanger developed the "dideory" technique for DNA sequencing. This techniques is used to determine the order of bases in a strand of DNA. He and his team tested their methods on an enterobacteria phage called PhiX174. They also eventually created a 5000 letter long sequence using the dideory technique. -
Kary Mullis
Kary Mullis discovered PCR (Polymerase Chain Reaction). This reaction allowed for the cloning of oligonucleotides. These nucleotides helped examine DNA, and the more oligonucleotides that you have, the more precise the examination. This is where the helpfulness of oligonucleotides comes into play. The idea came to him while he was driving at night, and when he woke up the next morning, there were diagrams of PCR everywhere he looked in his room. -
J. Craig Venter
Venter made his own first draft sequence of the human genome. His 'shotgun sequencing" was much faster and more effective than previous sequencing. He also created a team to transfect a cell with a synthetic chromosome.
