The Discovery of DNA Juenger, Josephine

Friedrich Miescher

1869

Friedrich Miescher extracted DNA from the cell nuclei of a white blood cell found on bandages he found in a clinic. He was able to conclude that DNA is not a protein, and it contains an abundance of nitrogen and phosphorus.

Frederick Griffith

1928

Originally trying to create a vaccine for pneumonia, Frederick Griffith Experimented harmless, R, cells and harmful, S, cells on mice. By heat killing the S cell, then injecting it with live R cells, he found that the S cells had shared its DNA with the R cells. This proved that DNA can transform other DNA.

Oswald Avery, Maclyn McCarty & Colin McCleod

1944

While studying Streptococcus pneumoniae, Avery, McCarty, and McCleod began an experiment by removing lipids, proteins, and nucleic acids from the S cell, or the lethal cell. Then, they tested each to see which part of the cell was responsible for transforming the R cells. They discovered that the nucleic acid, or DNA was the transforming principle. This experiment was able to prove Griffith’s discovery of DNA transformation, and that DNA is a molecule of heredity.

Erwin Chargaff

1949

After reading a paper by Oswald Avery, Erwin Chargaff was inspired and used the method of paper chromatology to separate adenine, thymine, cytosine, and guanine, which are the bases of DNA.In doing so, Chargaff discovered that that there is an equal amount of guanine to cytosine and thymine to adenine in DNA. Another of Chargaff’s discoveries is that the amount of adenine and guanine in DNA will vary depending on the species

Barbara McClintock

1950

While studying genetic mutation in corn and corn chromosomes with microscopes, Barbara was able to discover mobile genetic elements, which are genes that jump around to different chromosomes.

Alfred Hershey & Martha Chase

1951

Hershey and Chase conducted an experiment in which phage protein was labeled with a radioisotope of sulfur, while the phage DNA was labeled with a radioisotope of phosphorus. The labeled phage then would infect the bacteria. Each mixture was run through a blender. The radioactive sulfur was found outside the bacteria and the radioactive sulfur was found inside the bacteria. This proved that DNA is heredity material, contrary to the popular belief that protein in hereditary material.

Rosalind Franklin & Maurice Wilkin

1952

Franklin and Wilkins made major contributions in discovering the structure of DNA. Using X-ray crystallography, Franklin was able to take the first clear picture of DNA, known as Photograph 51. Using this, they discovered a pattern in DNA and that it was long. She also determined the density of DNA and its helical structure. Although not giving her credit, Watson and Crick used this information to develop the double helix DNA model.

Linus Pauling

1953

Using X-ray diffraction, Linus Pauling was able to discover the spiral structure of DNA proteins from his research on the cause of sickle cell anemia. Linus also proposed a triple helix model, which was later found incorrect. This gave him the name of founder of molecular biology. These pieces of information were major in later discoveries of DNA such as the double helix model developed by James Watson and Francis Crick.

James Watson & Frances Crick

1953

Using Photograph 51 and other research on the structure of DNA that was done by Rosalind Franklin, Watson and Crick were able to create a modeled structure of DNA that determined that DNA was a double helix. The model showed adenine paired to thymine, and cytosine to guanine, following the first of Chargaff’s discoveries and the bases on the inside of the helix, which was contrary to what most scientists believed at the time. It also included a sugar-phosphate backbone for each chain.

Matthew Meselson & Franklin Stahl

1957

Matthew Meselson and Franklin Stahl conducted an experiment to determine which of the three ways, semi-conservative, conservative, and dispersive. They did this by labeling old DNA and new DNA with isotopes. They then used E. coli to test the labeled DNA to find that DNA replicates in a semi-conservative way.

Frederick Sanger

1958

Studying insulin and ways to order the amino groups, Sanger was able to get a protein sequence that proved that proteins were ordered and therefore, genes and DNA are ordered.

Paul Berg

1972

Berg studied the tumor virus SV40, whose natural host is a monkey. While doing so, Berg placed DNA from a bacterium into the tumor virus’s DNA creating the first molecule that had two different species’ DNA.

Kary Mullis

1985

Kary Mullins invented a way of copying portions of DNA in a short period of time using a method known as PCR. He heated ingredients that included a DNA template, two oligonucleotide primers, nucleotides, and a polymerase enzyme. This causes the DNA template to separate, primers to fix to the separated DNA strands, and finally the polymerase enzyme can add nucleotides to the primers, creating copies of the DNA strands. In only a few minutes, this method can create over a billion duplicates.

J. Craig Venter

1995

J. Craig Venter was the first person who sequenced the human genome. He did this at the company he started, called Celera Genomics. He used the shotgun technique which deciphers small portions of genomic sequence, which then will be put together to create a whole genomic sequence.