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Gregor Mendel
Gregor Mendel is known to us as the “father of modern genetics”. He discovered the basic principles of heredity through experiments in a garden.
In around 1854, Mendel began his research on transmission of hereditary traits in plant hybrids. With the cross-fertilized pea plants that he used, he was able to come to his most important conclusions: Law of Segregation and the Law of Independent Assortment. -
Thomas Hunt Morgan
Thomas Hunt Morgan used the fruitfly Drosophila to study genetics. He noticed mutants forming, which allowed him to determine the precise behavior and exact localization of genes Morgan founded the idea of sex-linked traits and that spontaneous mutations occurred frequently in flies. He developed the theory of linear arrangement of the genes in the chromosomes. -
Frederick Griffith
Frederick Griffith was studying a bacterium that causes pneumonia in mammals. When he mixed a dead pathogenic strain and a living nonpathogenic strain, some of the living cells became pathogenic. The newly acquired trait of pathogenicity was inherited by all the descendants of the transformed bacteria as well. DNA was not discovered yet during this time. He called it transformation, which is now defined as a change in genotype and phenotype due to the assimilation of external DNA by a cell. -
Oswald Avery
Avery and his coworkers discovered that a cell’s genetic material is carried by DNA and that it could altered through transformation. His research led to understanding the genetic code.
Their experiment began with cultures of heat-killed S cells and they purified the transforming principle by washing away, separating, or enzymatically destroying the other components.
They obtain highly purified transforming principle in small amounts that they could analyze through other tests and identify it. -
Erwin Cargaff
Erwin Chargaff discovered that DNA is the primary constituent of the gene, helping create different approach to studying heredity.
He test the idea the DNA could be a primary constituent of the gene.
He fractioned out nuclei from cells, isolated the DNA form the nuclei and broke it down into nucleic acids, then used paper chromatography to separate the purines and the pyrimidines. He exposed the separated components to ultraviolet light.
He determine how much of each bases were present in DNA -
Rosalind Franklin and Maurice Wilkins
Rosalind Franklin produced diffraction images of DNA and determined that DNA can exist in two different forms. She also discovered that the phosphate groups must be on the outside and one of the two forms looked like a helix. Wilkins believed that it was a helix, but Franklin did not want to confirm this theory yet. Wilkins showed Rosalind’s x-ray to James Watson and Francis Crick without her permission. -
Alfred Hershey and Martha Chase
Alfred Hershey and Martha Chase performed an experiment showing that only one of the two components of T2 actually enters the E. coli cell during infection. They used different radioactive isotopes to tag the protein and DNA in batches of T2. Separate samples of nonradioactive E. coli cells were infected with the batches of T2. The DNA entered the cells, proving that nucleic acids are the hereditary material. -
James Watson and Francis Crick
Using Chargaff’s discoveries, James Watson and Francis Crick determine the structure of DNA. They proposed a double helix structure in conclusion in 1953.
The model explained how DNA replicates and how the hereditary information is coded.
They shared the Nobel Prize in Medicine in 1962.
