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Discovery of dna timeline

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Leya Conard

on 28 April 2015

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Transcript of Discovery of dna timeline

Friedrich Miescher

Experiment:
After getting pus bandages from hospitals, Miescher used alkaline to obtain lysed nuclei. Once he received the cell nuclei, Miescher nuclein, a unique chemical substance, and isolated it.
Martha Chase & Alfred Hershey
Year Published:
1952
Oswald Theodore avery
Results and Conclusion:
By the end of his study, Avery concluded that DNA is the transforming principle and genes are composed of DNA.
Erwin CHargaff
Rosalind Franklin & wilkins
Frederick Griffith

Experiment:
Griffith's experiment focused on two main strains of Pneumococcus, S (smooth) and R (rough). Because the S strain is infectious, when injected into mice they develop pneumonia and die, unlike the R strain. Next, in order to kill the bacteria, Griffith heated the S strain and when injected into the mice they did not die. Then, Griffith injected a heated S and R strain into the mice and they died.
Discovery of dna timeline
Results and Conclusion:
Miescher found that nuclein is high in phosphorous which could possibly mean nuclein was the cellular storehouse of a certain atom.
DNA and Cells Now:
This contributed to what we now know about DNA because his discovery helped Phoebus Levene study the structure and function of nucleic acids.
Year Published:
1871
Year Published:
1928
Results and Conclusion:
When Griffith inspected the blood the last group of mice, he found that the live S strain had reappeared. Griffith concluded that the R strain transformed into the S strain by some "principle."
DNA and Cells Now:
This has affected what is known about DNA today because it helped Avery with his discoveries. It also informed other scientists that there is a transforming factor and they should be aware of it while they're doing their experiments.
Year published:
1944
Experiment:
Avery based his experiments off of Griffith and his results from the pneumonia mouse experiment. His goal was to identify the transforming principle. Unlike Griffith, Avery used test tube assays during his testing. He found the transforming principle was in the lysate from the S strain. Avery made a sugar coat-less S lysate, but it was still able to transform, as well as his protein-less lysate and RNA-less solution. Finally, the DNA solution was tested and was unable to transform.
DNA and Cells Now:
This is important to what we now know about DNA because it answers the question from Griffith's experiment and allows other scientists to acknowledge that DNA is the transforming factor.
Year Published:
1950
Experiment:
Inspired by Oswald Avery's discovery, Chargaff decided to do some studies himself. He isolated DNA from four different organisms, calf thymus, beef spleen, yeast, and Tubercle Bacillus. Then, he measured the levels of the four nitrogenous bases, Adenine, Thymine, Cytosine, and Guanine.
Results and Conclusion:
By the end of his study, Chargaff councluded that DNA has a 1:1 ratio of pyrimidines and purine bases, or in other words, the amount of Adenine is equal to the amount of Thymine and the amount of Cytosine is equal to the amount of Guanine. This is known as Chargaff's base pairing rules or principles.
DNA and Cells Now:
This affects what we now know about DNA because in order to accurately study DNA its essential to know and understand the structure and all of its parts.
Year published:
1952
Experiment:
Franklin focused on finding the structure of DNA using a technique called X-ray diffraction. X-ray diffraction is the scattering of X-rays by the regularly spaced atoms of a crystal, used to determine the structure of the crystal.
Results and Conclusion:
Franklin's famous Photo 51 revealed very important details that have allowed other scientists to develop the structure of DNA. The X shaped in the photo suggest that DNA strands twist around each other into a helix. The picture also shows the nitrogenous bases are near the middle and there are two strands because of the angle of the X.
DNA and Cells Now:
This discovery was the key to unlocking the structure of DNA because other scientists like Watson and Crick were able to base their correct structure off of this photo.
Experiment:
Their study was focused on viruses, nonliving organisms that can infect living organisms, specifically bacteriophage. Bacteriophage are viruses that inject themselves into the bacteria. Their goal was to learn if these viruses were made of protein or DNA. They did this by growing viruses with isotopes of phosphorus-32 and sulfur-35. These substances were used as markers, meaning if 35 S was found in the bacteria then it would mean protein was injected, where as if 32 P was found in the bacteria then it would mean DNA was injected.
Results and Conclusion:
After testing, the scientists found that nearly all radioactivity in the bacteria was from 32 P, therefore they concluded DNA was the genetic material of the bacteriophage virus.
DNA and Cells Now:
This has affected what we now know about DNA because it emphasizes the idea that DNA is genetic, even in viruses, which can ultimately help fight viruses.
James Watson and
Francis crick
Year published:
1953
Experiment:
Watson and Crick had been struggling to build a correct model of the structure of DNA, that is until they saw Franklin's Photo 51. Once they saw the X shaped pattern they immediately were able to construct an accurate model of the double helix DNA structure.
Results and Conclusion:
The scientists concluded that DNA contains a double helix. They used lots of math to calculate that there are about 10 bases per helical repeat. The pair also discovered DNA has an anti-parallel structure.
DNA and Cells Now:
This relates to what we know about DNA know because the structure of DNA is essential to understanding what DNA is and how it works.
Matthew meselson & franklin stahl
Year published:
1958
Experiment:
In their experiment, the scientists grew E. coli in culture with 15N (isotope of the nitrogen atom), and was soon incorporated into the bases of DNA as the bacteria grew. This group was then transferred to a culture with 14N (normal nitrogen). After taking samples from each culture, the scientists isolated and dissolved the DNA from the bacterial cultures in a salt solution. Then, they centifuged the DNA and were able to find the greatest density based on the number of salt molecules.
Results and Conclusion:
The results were 15N sank further in the salt gradient than 14N. The results supported the semi-conservative DNA replication model. By using the nitrogen isotopes and density gradient centrifugation, Meselson and Stahl were able to prove DNA is replicated semi-conservatively.
DNA and Cells Now:
This contributed to what we now know about DNA because understanding how it replicates is important when studying DNA.
Year Published:
1958
Experiment:
Their experiment was based on Neurospora Crassa (red bread mold) and their goal was to find the nutritional mutants if they mutated a gene that cannot grow on minimal medium. By using X-rays on the Neurospora culture, they were able to discover that the 299th culture did not grow on the minimal medium and the first Neurospora mutant couldn't make vitamin B.
Results and Conclusion:
By the end of their study, the scientists concluded that genetic mutations affect pathways for vitamin amino acids. They also found that one gene is responsible for one protein because each mutated gene only affected a part of the metabolic pathway.
DNA and Cells Now:
This affects what we know about DNA now because when scientists study it they need to be making the right calculations and for that they need to know that one gene is responsible for one protein.
Marshall Nirenberg
Year Published
: 1961
Experiment:
Nirenberg based his experiment off the triplet codon hypothesis. He used an extract of E.coli to make a synthetic mRNA composed of Uracil and added it to poly-uRNA extract along with radiolabeled amino acids.

Results and Conclusion:
Nirenberg found polypeptides made up of the amino acid phenylalanine and therefore was able to conclude UUU (three uracils) codes for phenylalanine. Similarly, he found CCC codes for proline, AAA codes for lysine, and GGG does not produce a protein.
DNA and Cells Now:
This discovery is one of the most useful when trying to decipher the genetic code. Scientists are now able to figure out the proteins of a cell which affect how it works.
George Beadle & Edward tatum
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