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Friedrich Miescher
His goal was to figure out the building block of life. He was studying white blood cells and came across another substance with different properties that did not match those of proteins. He found out that the new substance is fundamentally different from proteins and is located in the cell's nuclei, therefore naming it Nuclein. He determined that this new molecule is different from proteins because its rich in nitrogen and phosphorus. Miescher is the first to identify DNA as a distinct molecule. -
Frederick Griffith
Griffith conducted an experiment where he had two types of cells, R cells(non lethal) and S cells(lethal), and injected them into mice trying to create a vaccine for pneumonia. During his experiment, he discovered that heat destroyed the ability of S cells to cause pneumonia, but it did not destroy its hereditary material, including what specifically killed the mice.That material can be transferred from the dead S cells into the R cells, who then can put it to use. He calls this transformation. -
Barbara McClintock
She discovered that genes could move from place to place on a chromosome/segments of DNA can be moved to other regions of the genome, and that these movements could directly influence the activity of other genes. -
Oswald Avery, Maclyn McCarty & Colin McCleod
Their goal was to prove Griffith's experiment. They termed the substance from Griffith's experiment as the 'transforming principle'. They made an extract of S cells that contained only lipids, proteins, and nucleic acid. Once they added nucleic acid degrading enzymes to the extract, it destroyed the extract's ability to transform cells. When they added protein and lipid destroying enzymes, the extract was still able to transform R cells. This finally proved that DNA is the transforming molecule. -
Erwin Chargaff
Chargaff discovered the base pairing of nitrogen bases in DNA. Created a rule called "Chargaff's Rule". The rule states that in any given sample of DNA, there will be equal amounts of adenine and thymine, and equal amounts of guanine and cytosine. He also discovered that the DNA of different species differ in the proportions of adenine and guanine/ thymine and cytosine. -
Alfred Hershey & Martha Chase
Hershey and Chase proved that DNA satisfies the first property of a hereditary molecule: It transmits a full complement of hereditary information. They experimented with bacteriophage which is a virus that infects bacteria and creates new virus particles once injected. This experiment also proved that bacteriophage injects its DNA into bacteria cells in order to spread. Their main goal was to determine the composition of the hereditary material, which was DNA not proteins. -
Rosalind Franklin & Maurice Wilkins
Wilkins obtained the first clear crystalline x-ray diffraction patterns from DNA fibers. Franklin on the other hand made the first x-ray diffraction image of DNA as it occurs in cells, named photo 51. This x-ray crystallography of DNA indicated the helical shape of DNA. Wilkins worked on the same idea and shared the information. -
Linus Pauling
Pauling discovered the alpha helical nature of protein structure. He shared his published model of DNA at Cambridge University. His model proposed a a 3 stranded helix with the bases on the outside. He is known as the founder of molecular biology due to his discovery of the spiral structure proteins. -
James Watson & Frances Crick
They discover the structure of DNA (double helix). They made many models from scrap-metal and other objects in order to create the first accurate visual of DNA. Watson and Crick used Rosalind Franklin's data to create the first ever correct model of DNA. In order to make the model seem like an actual DNA molecule, they included two sugar-phosphate chains running in opposite directions, and paired bases inside. They also thought that hydrogen bonds held together the nitrogen bases. -
Matthew Meselson & Franklin Stahl
Meselson and Stahl proved Semi Conservative Replication. Semi Conservative Replication states that parent DNA opens like a zipper and forms two new strands - each contain 1 parent and 1 daughter strand. The experiment they preformed to prove Semi conservative Replication verified Watson and Crick´s model for the structure of DNA, which represented DNA as two helical strands wound together in a double helix. The experiment enabled researchers to explain how DNA replicates. -
Paul Berg
Berg created the first man-made recombiant DNA. His experiment involved splicing DNA from the bacterial virus lambda into the DNA of the simian virus SV40. Recombiant DNA is the joining together of two or more DNA molecules from different species that are inserted into a host organism to produce new genetic combinations. -
Frederick Sanger
Sanger developed "rapid DNA sequencing" which is a technique known as the Sanger method. Its used to determine the sequence of nucleotide bases in a piece of DNA. In Sanger sequencing, the target DNA is copied many times, making fragments of different lengths. Fluorescent "chain terminator" nucleotides mark the ends of the fragments and allow the sequence to be determined. -
Kary Mullis
Mullins invented the polymerase chain reaction.The Polymerase chain reaction is a technique used to make numerous copies of a specific segment of DNA quickly and accurately. This process can produce more than a million copies of the DNA sequence. -
J. Craig Venter
Venter determined the genomic sequence of a bacteria that causes earaches and meningitis in humans. This was the first time that the complete sequence of a free-living organism had been deciphered. In 1998, he started sequencing the human genome and finished the HGP (Human Genome Project) In 2003. The sequencing of the human genome was then completed.
