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SCIENCE AS A PROCESS

SCIENCE AS A PROCESS. http://profiles.nlm.nih.gov/CC/A/A/A/Z/_/ccaaaz~.jpg. WHAT DO WE KNOW ABOUT DNA? HOW DID WE FIGURE IT OUT?. http://en.wikipedia.org/wiki/Rosalind_Franklin. http://www.mun.ca/biology/scarr/Chase_&_Hershey_1953.jpg.

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SCIENCE AS A PROCESS

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  1. SCIENCE AS A PROCESS http://profiles.nlm.nih.gov/CC/A/A/A/Z/_/ccaaaz~.jpg WHAT DO WE KNOW ABOUT DNA? HOW DID WE FIGURE IT OUT? http://en.wikipedia.org/wiki/Rosalind_Franklin http://www.mun.ca/biology/scarr/Chase_&_Hershey_1953.jpg http://www.3quarksdaily.com/.a/6a00d8341c562c53ef0120a6194d2f970c-600wi http://www.time.com/time/time100/scientist/profile/watsoncrick.html

  2. Archibald GARROD (1909) 1st to suggest genes dictate phenotypes through enzymes that catalyze specific reactions in cells Coined term “inborn errors of metabolism” Hypothesized that patients with alcaptonuria lack an enzyme in metabolic pathway ALCAPTONURIA- “Black urine” disease Lack enzyme to break down alcapton Builds up in joints (osteoarthritis), heart valves, and kidney stones Excess excreted in urine http://www.nexusediciones.com/images/alcaptonuria04.jpg

  3. Frederick GRIFFITH (1928) • See the experiment Bacterial transformation of pneumonia bacteria in mice http://upload.wikimedia.org/wikipedia/en/thumb/f/f4/Griffithm.jpg/140px-Griffithm.jpg http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=glyco2&part=ch39&rendertype=figure&id=ch39.f1

  4. Oswald AVERY, Colin MACLEOD, and Maclyn MCCARTY (1944) Repeated Griffith’s experiment but added enzymesto destroy different kinds of molecules. . . . DNA is the transforming molecule http://profiles.nlm.nih.gov/CC/A/A/A/Z/_/ccaaaz~.jpg

  5. George BEADLE and Edward TATUM (1940’s)“one gene-one enzyme” http://www.nauba-aloke-bangla.com/EBook/Projukti-o-Biggan/top100/Beadle_Tatum.jpg Experiment images from: Campbell and Reece AP Biology Neurospora bread mold mutants Each lacks different enzyme in biochemical pathway If add missing substance, mold is able to grow

  6. Alfred HERSHEY and Martha CHASE (1952) • See their experiment DNA = genetic code molecule http://osulibrary.oregonstate.edu/specialcollections/coll/nonspcoll/catalogue/portrait-hersheychase-600w.jpg https://www.msu.edu/course/lbs/333/fall/images/HERSHEY2.gif

  7. ROSALIND FRANKLIN and MAURICE WILKINS Analyzed DNA with X-ray crystallography to try and determine its structure 1953 - JAMES WATSON & FRANCIS CRICK used Rosalind Franklin’s X-ray crystallography images (PHOTO 51) to come up with alpha helix model for the structure of DNA http://en.wikipedia.org/wiki/Rosalind_Franklin http://www.time.com/time/time100/scientist/profile/watsoncrick.html

  8. http://www.pnas.org/content/101/52/17889/F1.medium.gif Matthew MESELSON and Franklin STAHL (1958) • See their experiment DNA copies by semi-conservative model http://en.wikipedia.org/wiki/File:DNAreplicationModes.png

  9. Images from: http://instruct1.cit.cornell.edu/courses/biog105/pages/demos/106/unit01/6.dnareplicationmodels.html MESELSON & STAHL Grew bacteria for many generations in radioactive (heavy) 15N . . . so all DNA is heavy Then grow in 14N, centrifuge as generations divide, and check to see where heavy DNA ends up http://www.sumanasinc.com/webcontent/animations/content/meselson.html

  10. MESELSON & STAHL Can tell which model it is by the banding patterns of DNA molecules SO WHAT ? Provided evidence for SEMI-CONSERVATIVE REPLICATION MODEL http://www.sumanasinc.com/webcontent/animations/content/meselson.html

  11. Telomeres protect DNA from being degraded Telomeres become shorter with each replication; shorter in older cells Telomerase enzyme lengthens telomeres Stem cells, germ cells making gametes, and cancer cells have increased telomerase activity 2009Nobel PrizePhysiology/Medicine Discovery of Telomeres Jack Szostak Carol Greider Elizabeth Blackburn.

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