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Friedrich Miescher
Miescher was the first person to identify and isolate DNA. He was working in a lab to study medicine when he researched white blood cells. In the pus of these cells, he saw nucleic acids, which he called "nuclein" because it is from the nucleus. He said nuclein was different from other molecules because it contained phosphorus. He suggested that nuclein was the molecule of heredity. Before this, DNA was not yet discovered and he showed that there is something in cells not made purely of proteins -
Erwin Chargaff
Erwin Chargaff was a chemist who started studying DNA after hearing about the Avery-MacLeod-McCarthy experiment that suggested that DNA was the heredity code passed from parent organisms to offspring. Chargaff discovered that the proportions of nitrogenous bases in DNA of organisms is what made species different and that the amount of purines in a DNA molecule are equal to the amount of pyrimidines. Previous to Chargaff, it was believed that the order of bases was the same in any organism. -
Rosalind Franklin
Franklin, a scientist who studied Natural Sciences, started learning X ray diffraction and started to use it to study coal atomic structure. She studied DNA with this method and discovered 2 types of DNA(B type- wetter, in living cells and A type-drier). While working with x ray diffraction, she took Photo 51 of B DNA; a picture that showed DNA structure. Before Franklin's picture, the arrangement of a DNA molecule was not known, nor was the fact that DNA can be in more than one form. -
Hershey and Chase
These scientists set out to prove that DNA is the genetic material. They created an experiment using a virus, phage, to infect a bacteria cell. The phage was coated in protein that stayed on the outside of the bacteria cell, while the phage's DNA entered the cell.When the bacteria cell shook, the protein coat broke away, but the DNA remained inside the cell and new phage viruses grew, showing that DNA is the genetic material. Before this, it was thought that proteins were the genetic material. -
Watson and Crick
These scientists wanted to know what DNA looked like, so they began listening to seminars and constructing 3D models of what they thought DNA to look like. After seeing Franklin's X ray, they knew what to build. They built an accurate 3D DNA model that explained Chargaff's Rule and the x pattern that Franklin saw in her x ray. They also discovered that hydrogen bonds held nitrogenous bases together, hence how each helix in the double helix connected.Before this, the structure of DNA was unknown. -
Meselson and Stahl
These 2 scientists wanted to figure out how DNA replicated. They designed an experiment using bacteria and soaked it in different amounts of a certain nitrogen found in DNA to watch the bacteria DNA after division. This experiment proved the semi-conservative model to be correct, which stated that daughter DNA cells had half parent DNA and half new DNA, being identical to the parent. This added to Watson and Crick's model by showing how the molecule splits to make daughter cells. -
Citations
"Francis Crick." Famous Scientists. famousscientists.org. 17 Aug. 2016. Web. 1/22/2017 "Rosalind Franklin." Famous Scientists. famousscientists.org. 12 Aug. 2016. Web. 1/22/2017 Chapter 16 & 17 Molecular Genetics. Digital image. Wikispaces. Tangient, 2017. Web. "Concept 15 DNA and Proteins Are Key Molecules of the Cell Nucleus." Friedrich Miescher :: DNA from the Beginning. DNA Learning Center, Cold Spring Harbor Laboratory, 2002-2011. Web. 22 Jan. 2017. -
Citations
Digital image. Blogspot.com. N.p., 11 Feb. 2012. Web. 23 Jan. 2017. Digital image. The Scientist. The Scientist, 06 July 1998. Web. 23 Jan. 2017. Griffiths, Anthony JF. "DNA: The Genetic Material." An Introduction to Genetic Analysis. 7th Edition. U.S. National Library of Medicine, 01 Jan. 1970. Web. 23 Jan. 2017. "Hershey+and+Chase+Experiment." Hershey+and+Chase+Experiment. The McGraw-Hill Companies, Inc., n.d. Web. 23 Jan. 2017. -
Citations
"Meselson & Stahl, The Semi-Conservative Replication of DNA." IBiology. IBiology, 05 Mar. 2016. Web. 23 Jan. 2017. Miller, Kenneth R., and Joseph S. Levine. Miller & Levine Biology. Boston, MA: Pearson, 2012. Print. "Nucleic Acid." Nucleic Acid: Introduction. Sandbox Networks, Inc., 2000-2017. Web. 23 Jan. 2017. Revealing DNA as the Molecule of Life. Digital image. Yourgenome.org. N.p., 13 June 2016. Web. 23 Jan. 2017. -
Citations
Structure of Life. Digital image. Lebbeus Woods. N.p., 30 Aug. 2010. Web. Structure of Life. Digital image. Lebbeus Woods. N.p., 30 Aug. 2010. Web. 23 Jan. 2017. Sziegler. "Friedrich Miescher - Discoverer of DNA." Friedrich Miescher Institute of Biomedical Research. FMI Basel Switzerland, 2017. Web. 23 Jan. 2017. -
Citations
See J. D. Watson, The Double Helix: A Personal Account of the Discovery of the Structure of DNA (1968) and DNA: The Secret of Life (2003); R. L. Adams et al., ed., The Biochemistry of the Nucleic Acids (1986); V. K. McElheny, Watson and DNA: Making a Scientific Revolution (2003); I Rosenfield et al., DNA: A Graphic Guide to the Molicule that Shook the World (2010). "Erwin Chargaff." Famous Scientists. famousscientists.org. 9 Aug. 2016. Web. 1/22/2017
