Dna Genetics Key People

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Gregor Mendel

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1822-1884 - Gregor Mendel, who was a monk, played a very important role in the discovery of genes and heredity. He is considered to be the father of genetics with his famous experiment about peapods that explained the patterns of inheritance. The short monograph, Experiments with Plant Hybrids, in which Mendel described how traits were inherited.

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Robert Feulgen

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1884-1955 - German chemist who in 1914 developed a method for staining DNA now known as the Feulgen stain and he discovered that DNA is located in the chromosomes. Feulgen stain is a staining technique discovered by Robert Feulgen and used in histology to identify chromosomal material or DNA in cell specimens. It depends on acid hydrolysis of DNA, therefore fixating agents using strong acids should be avoided.

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Johann Friedrich

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1869 identifies a weakly acidic substance of unknown function in the nuclei of human white blood cells. This substance will later be called deoxyribonucleic acid, or DNA

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P.A. Levine

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Discovered phosphate groups, five carbon sugars and nitrogen containing bases (purines and pyrimidines). Also analyzed the components of the DNA molecule. He found it contained four nitrogenous bases: cytosine, thymine, adenine, and guanine; deoxyribose sugar; and a phosphate group. He concluded that the basic unit (nucleotide) was composed of a base attached to a sugar and that the phosphate also attached to the sugar. He (unfortunately) also erroneously concluded that the proportions of bases were equal and that there was a tetranucleotide that was the repeating structure of the molecule. The nucleotide, however, remains as the fundamental unit (monomer) of the nucleic acid polymer. There are four nucleotides: those with cytosine (C), those with guanine (G), those with adenine (A), and those with thymine (T).

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Sir William Henry Bragg and Sir William Lawrence

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1912 – discover that they can deduce the atomic structure of crystals from x-ray diffraction patterns, this helps Watson and Crick.

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Frederick Griffith

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– 1920’s – studied disease-causing strain of pneumonia causing bacteria, and a strain that did not cause pneumonia, the S strain and R strain. The S strain had a capsule around it and the R strain did not. He was able to induce a nonpathogenic strain of bacterium Streptococcus pneumoniae to become pathogenic.

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Avery, MacLeod, and McCarthy

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1928 – mystery of inheritance, took up the experiment by Griffith. Bacteria could transform other bacteria by giving them new genetic characteristics through a liquid medium, therefore, if bacteria transform when an organic molecule is placed in a liquid with them, then that molecule holds genetic info.

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Luria Delbruck Experiment

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1943
also called Fluctuation Test, in bacteria, genetic mutations arise in the absence of selection, and therefore Darwin’s theory of natural selection acting on random mutations applies to bacteria as well as higher organisms, won the Nobel Prize in 1969. Studied Phages in Cold Springs Harbor, and concluded that DNA was responsible for the genes that are made, and not the protein coat

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Erwin Chargaff

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1950, Chargaff’s rules - analyzed the base composition of DNA composition in a number of organisms. He reported that DNA composition varies from one species to another. Such evidence of molecular diversity, which had been presumed absent from DNA, made DNA a more credible candidate for the genetic material than protein. Also, Chargaff found that a peculiar regularity in the ratios of nucleotide bases. In the DNA of each species he studies, the number of adenines approximately equaled the number of thymine, and the number of guanines approximately equaled the number of cytosine. In human DNA, for example, the four bases are present in these percentages: A=30.9% and T=29.4%; G=19.9% and C=19.8%. The A=T and G=C equalities, later known as Chargaff's rules, helped Watson and Crick to discover the structure of DNA.

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Hershey (1908-1997) and Chase Blender Experiment

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1952, wanted to know whether DNA or proteins were responsible for transferring genetic materiel. Had sulfur labeled protein capsule, and phosphorus DNA core. They let the 2 bacteriophages infect bacteria, and blended them, which removed the bacteriophages after it had injected the genetic materiel. They put them in a centrifuge to separate the materials, and found phosphorus in the cells, supporting that DNA codes for genes. Did this in the Cold Spring Harbor in New York, and worked with both Luria and Delbruck in 1940.

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Rosalind Franklin

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took famous photo 51, which is an x-ray diffraction image of DNA, taken in 1952, and shows the double helix structure. She worked at Kings College
London with Raymond Gosling under John Randall. Kings College London is the U of London, and founded in the early 19th century.

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Francis Crick (1916-2004) and James Watson (1928)

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worked in the Cavendish Lab at Cambridge, and announced the discovery of DNA at Eagle Hotel. Watson was 21 years old, had a PhD, and was a genius with s small case of autism. Crick was 27 years old, and they worked together because they collaborated well and threw ideas back and forth at each other. When one person’s idea was wrong, the other one would be there to correct them and keep them straight. They pieced the puzzle of DNA together by researching other people’s data and learning about other discoveries. They were supposed to be working on Hemoglobin, but genetics interested them. They traveled around listening to lectures of others, and gathering information form other scientists at the time.

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Linus Pauling

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1901 – 1994 – won the 1952 Nobel Prize, and son Peter Pauling was there to accept prize. He had multiple grants, and had many people working under him, but had his passport revoked so he could not leave the country.

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Maurice Wilkins

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1916 – 2004 – worked with the Manhattan Project to create a nuclear bomb, and approached genetics in a new way, and was very methodical. He did not accept everything that was told to him about genetics.

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Purines and Pyrimidines

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Adenine and Guanine are Purines - they are larger and have a double ring. Thymine and Cytosine are Pyrimidines - they are smaller and have a single ring. The nucleotides have three components, a pentose sugar, an amino base (the A, T, C, G), and a phosphate group