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Date Created: 01/31/16
Melika Barshooi BIO 1801 Brandon Stanton October 22, 2015 Deoxyribonucleic Acid (Nobel Prize in Chemistry 2015) Summary The deoxyribonucleic acid strands were originally created with 23 chromosomes from the sperm and 23 chromosomes from the egg. Combined, the chromosomes form the original genome; subject to cell division increasing that number. After the fertilized egg divides, the DNA was copied and the daughter cell received a set of chromosomes. The cell division continued the same process and somehow managed to keep the recent copy incredibly similar to that of the original genome. Thomas Lindahl, Paul Modrich, and Aziz Sancar have received the Nobel Prize in Chemistry for their groundbreaking research. Lindahl began in the late 1960’s with the question of how stable DNA is. He tested RNA under heat and found that the molecules degraded rapidly. Knowing that RNA is more delicate than DNA, he tested the DNA and found that while the molecules degraded much slower, there was still a noticeable difference. This stumped all scientists, as the DNA undergoes many injuries on a daily basis. Lindahl then began testing bacterial DNA for the repair of enzymes. After experimenting, he realized that there must be protection for DNA from the damaged remains of cytosines. Sancar’s study began on the subject of UV DNA repair. This stemmed from the curiosity of how bacteria is instantly healed by visible blue light after large amounts of deadly radiation. He eventually established nucleotide excision repair, which repairs DNAinjuries caused by UV radiation or carcinogenic substances. As stated by the National Academy of Sciences, “To Sancar’s surprise, the complex did not just nick the DNA near the damage, which was a popular working model at the time, but instead made a cut on each side to excise a chunk of DNA (7). Sancar termed the enzyme for this activity excision nuclease, or excinuclease. With Rupp’s help, Sancar also invented a method for identifying plasmidencoded proteins through bacterial cells called maxicells” ("Correction for Blelloch Et Al., Inaugural Article: Nuclear Cloning of Embryonal Carcinoma Cells”). He then continued to practice on humans, learning that while the system in humans is more complex, they all function in a similar sense. He also developed an interest in photolyase, which led to his discovery that the human equivalent to photolyase helps set the circadian clock. Modrich focused most of his scientific study on the enzyme Dam Methylase. When comparing this enzyme to the methyl groups, he discovered that they help a restriction enzyme to cut the DNA strand at a certain location. When faced with his conclusion in the crossed paths of different signalling functions for DNA, he stated that DNA mismatch repair is a natural process that corrects mismatches that occur when DNA is copied, recognizing the defect strand through methyl groups. As stated on his faculty and research page through Duke University, “Mismatch repair is a mutation avoidance system that stabilizes the genome by correcting DNA biosynthetic errors, by blocking recombination between diverged DNA sequences, and in the case of human cells, by targeting for death cells that have suffered certain types of DNA chemical damage” ("Paul L. Modrich (Primary)". This breakthrough discovery led to cloning and mapping enzymes for the repair process. Several years later, he was able to recreate the complex molecular repair mechanism. Work Cited "Correction for Blelloch Et Al., Inaugural Article: Nuclear Cloning of Embryonal Carcinoma Cells, PNAS 2004 101:1398513990."Proceedings of the National Academy of Sciences 101.39 (2004): 14305. Web. "Paul L. Modrich (Primary)." Paul L. Modrich (Primary). N.p., n.d. Web. 22 Oct. 2015.
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