Send the link below via email or IMCopy
Present to your audienceStart remote presentation
- Invited audience members will follow you as you navigate and present
- People invited to a presentation do not need a Prezi account
- This link expires 10 minutes after you close the presentation
- A maximum of 30 users can follow your presentation
- Learn more about this feature in our knowledge base article
Discovery Of DNA Timeline
Transcript of Discovery Of DNA Timeline
In 1950 Erwin Chargaff published his discovery that in DNA the number of guanine units equals the number of cytosine units, and the number of adenine units equals the number of thymine units. This became known as Chargaffs rule. He found this by isolating the DNA from different organisms and measured the levels of each of the four nitrogenous bases.
Martha Chase & Alfred Hershey-1952
In 1952 Martha Chase & Alfred Hershey discovered that DNA is the genetic material. The scientists used radioactive sulfur and phosphate to identify proteins and DNA. The viruses attacked the bacteria cells and were then separated from bacteria and smaller particles. The experiment showed that most of the bacterial DNA remained in the cells while their proteins were released outside. They concluded that the protein helped to inject the DNA of the virus into the bacterial cell, therefore DNA played a role in growth and reproduction within the cell of the bacteria. If they had not discovered this biology may still think that genetic information was a protein and that DNA only played a role in inheritance. Thus we would not know that DNA is the genetic material.
James Watson & Francis Crick-1953
1953 James Watson & Francis Crick built the first accurate model of DNA. The scientists used data published by Erwin Chargaff to conclude that the nitrogenous bases had to be arranged in pairs and experimented for a long time until finally discovering that the double helix was the shape that corresponded with data found by previous experiments such as Rosalind Franklin’s. Watson and Crick organized data that corresponded to the structure of the macromolecule for many years until being shown Rosalind Franklin’s x-ray diffraction photographs of DNA, which they were able to comprehend in a different way than Franklin and identify the structure, then built a model of it. This discovery is how we know that DNA is shaped like a twisted ladder.
In 1956 Arthur Kornberg discovered DNA polymerase, which scientists could use to make copies of DNA. Kornberg first perfected techniques for synthesis of two enzymes which are involved in the production of molecules rich in energy that were are used in the body. He used a chemical reaction that separates phosphate from the molecule which is used to synthesize proteins. Kornberg recognized this reaction was similar to DNA synthesis. He later used Watson and Crick’s work as well as techniques for RNA synthesis to discover the enzyme which responsible for DNA synthesis was in the bacteria E. coli. Kornberg was able to use this enzyme to produce biologically inactive DNA molecules, but still proved that the enzyme is used in the production of new DNA strands and that a single strand of DNA can act as the foundation for new strands of nucleotides. Then, Kornberg succeeded in removing other enzymes from the DNA polymerase and, with the help of Robert Sinsheim, simplified the once complex enzyme. Which is now known to be used during DNA replication.
Paul Zamecnik & Mahlon Hoagland-1957
In 1957 Paul Zamecnik & Mahlon Hoagland discovered tRNA. They were focusing on how amino acids were activated prior to their incorporation in proteins. They found that the amino acids were first attached to a soluble RNA. Those amino acids were subsequently transferred to proteins in ribosomes. They later renamed them transfer RNA (tRNA) to better reflect its role. This ties into what we know that converts the codons into proteins.
Matthew Messelson & Franklin Stahl-1958
In 1958 Matthew Messelson & Franklin Stahl published their findings that DNA replicates semiconservatively. They grew several generations of E.coli in 'heavy' nitrogen medium, and extracted a DNA sample from these bacterial cells. They called this sample "generation zero" and prepared it for centrifugation. The result showed that the DNA in generation zero had a heavier density, that is was in the "heavy" form. after several more generations, showed that now a larger portion of the DNA had light density, synthesized from the first and second generations, and a smaller portion of DNA had intermediate density, sythesized from the heavy and light DNA. This proved the semiconservative hypothesis and was a major step in developmental biology research and what we know now about DNA replication.
In 1961 Marshall Nirenberg Marshall Nirenberg was the scientist who decoded the part of DNA that controls the synthesis of many protein molecules which are the basis for cells. His research involved studying the genetic code involvement in sequences for different amino acids. Nirenberg discovered how to determine each sequence patterns code for each of the 20 known amino acids. When Nirenberg began his work, it was already known that three nitrogenous bases carry information which codes for a single codon as well as the basic functions of RNA. Marshall used artificial RNA composed only of uracil, a RNA nucleotide, thus the codon was UUU. He then placed the RNA in a solution of bacteria with all components of a normal cell. The mixture resulted in the production of phenylalanine, suggesting that UUU coded for that amino acid. Nirenberg repeated this experiment for all of the possible combinations of nucleotides in a codon. Through this experiment, Nirenberg not only proved which amino acids code for which codon, but also that the bases must be in a certain order for the correct amino acid to be brought to the ribosome. Without his discovery we woud not know much about Translation.
In 1871 Friedrich Miescher discovered nuclein. He discovered it by taking pus from infections and researching the compostion of white blood cells. inside the nucleus he isolated a new molecule named nuclein. He found that nuclein was made up of hydrogen, oxygen, nitrogen and phosphorus and there was an unique ratio of phosphorus to nitrogen. If Friedrich did not find nuclein then the findings of it actually being nucleic acids would be non existant.
Source: "Concept 15 DNA and Proteins Are Key Molecules of the Cell Nucleus." Friedrich Miescher. Web. 02 Apr. 2016.
In 1928 Frederick Griffith published his results for his experiment on different pneumoniae strains in mice and found. That mice that were injected with a rough strain or a heat-killed smooth strain lived. But mice injected with a smooth strain or a rough strain and heat-killed smooth strain died. He recovered some live cells from the dead mice and noticed that the heat-smooth strain had converted the rough strain into live smooth strain. Frederick called this process the tranforming principle that one bacteria could transform into another. This lead to Oswald Avery's discovery that DNA is the transforming principle.
Source:"Animation 17: A Gene Is Made of DNA. :: DNA Learning Center." DNALC Blogs. Web. 02 Apr. 2016.
Source:"Erwin Chargaff, 1950 :: DNA Learning Center." DNALC Blogs. Web. 03 Apr. 2016.
Source:"Alfred Hershey and Martha Chase, 1952 :: DNA Learning Center." DNALC Blogs. Web. 03 Apr. 2016.
Source:"Concept 19 The DNA Molecule Is Shaped like a Twisted Ladder." Watson and Crick: 3-D Structure of DNA. Web. 03 Apr. 2016.
In 1951 Linus Pauling discovered the helix shape of protein. Using his theory of complementarity, in which enzyme reactions and how genes act as templates in the formation of enzymes are explained. Using this theory and the major discoveries of previous scientists, Pauling observed molecular abnormality and hereditary and their relationship. From his observations, he determined that sickle cell anemia is caused by a single mutation in a hemoglobin molecule, which transports oxygen through the bloodstream. Further research showed that the molecule has a significant structural change when it loses or gains an oxygen atom. In an attempt to learn more about the structure of hemoglobin and proteins in general, Pauling used x-ray diffraction photographs taken by William Astbury. However, Pauling found that the patterns were incorrect, but had already developed a molecular model for a hemoglobin molecule. The model depicted a helix with a chain of atoms wrapped around the central axis. This helped James Watson & Francis Crick build their model of DNA. If it wasnt for Pauling Watson & Crick may not have built the first accurate model of DNA.
Source:"Linus Pauling - Biographical." Linus Pauling - Biographical. Web. 03 Apr. 2016.
Source:"Concept 20 A Half DNA Ladder Is a Template for Copying the Whole." DNA Replication. Web. 03 Apr. 2016.
Source:"Concept 22 DNA Words Are Three Letters Long." Genetic Code, Translation. Web. 03 Apr. 2016.
Source:"Concept 21 RNA Is an Intermediary between DNA and Protein." RNA Transcription, Translation. Web. 03 Apr. 2016.
Source:"Concept 20 A Half DNA Ladder Is a Template for Copying the Whole." DNA Replication. Web. 04 Apr. 2016
"Concept 20 A Half DNA Ladder Is a Template for Copying the Whole." DNA Replication. Web. 03 Apr. 2016.
"Animation 17: A Gene Is Made of DNA. :: DNA Learning Center." DNALC Blogs. Web. 02 Apr. 2016.
"Erwin Chargaff, 1950 :: DNA Learning Center." DNALC Blogs. Web. 03 Apr. 2016.
"Alfred Hershey and Martha Chase, 1952 :: DNA Learning Center." DNALC Blogs. Web. 03 Apr. 2016.
"Concept 15 DNA and Proteins Are Key Molecules of the Cell Nucleus." Friedrich Miescher. Web. 02 Apr. 2016.
"Concept 22 DNA Words Are Three Letters Long." Genetic Code, Translation. Web. 03 Apr. 2016.
"Linus Pauling - Biographical." Linus Pauling - Biographical. Web. 03 Apr. 2016.
"Concept 21 RNA Is an Intermediary between DNA and Protein." RNA Transcription, Translation. Web. 03 Apr. 2016.
"Concept 19 The DNA Molecule Is Shaped like a Twisted Ladder." Watson and Crick: 3-D Structure of DNA. Web. 03 Apr. 2016.