Dna history Essays

Dna history Essays Dna history Essay Dna history Essay The history of DNA structure discovery(sec. 4. 1): 1869- Johan miescher studies the nuclei of white blood cells(isolated th material using HCL and digestive proteins Named the substance nulclein and also found the material was rich in nitrogen and phosphorus. 919-Pheobus levene Discovered that DNA was made of chains of nucleotides *see nucleotide structure* 1920 DNAVSRNA * see chart Thought that 4 nucleotides were connected in the same repeated pattern protein gas 20 amino acids which could be combined in many combinations 1928- Frederick Griffith studied tho starins of pnuemococccus bacteria Rough strain-nonvirulent -Injection into mouse did not result in death smooth -injection caused death conclusion; some factor from the dead, virulent smooth strain transformed rthe living non-virulent rough strain. Non virulent rough strain picked up DNA becoming virulent. 1930-Joachim hammerling *see image in notebook* nucleus controls phenotypic properties of algae Avefry continued Griffiths w ork: purified chemicals from the heat-killed virulent bacteria, including DNA transformed non-virulent bacteria with each chemical into viruent only DNA resulted in death of the mouse Conclusion: transforming agent is DNA, thus DNA carries information to change living cell. 944-Avey, McCarty, and MacLeod Continued Griffiths work with pnemococcus see notebook* 1940s-Joshua Lederberg demonstrated bacterial conjugation -bacteria can exchange DNA Baccteria have no nucleus or chromosomes. 1940s- Edwin Chargaff For all organisms A=T and G=C (chargaffs rule) Organsisms with more Gs and Cs tend to be more complex (3 h-bonds) 1952-Hersey chase Conducted experiments to show definitive data to show DNA is the hereditary material. Bacteriophage used to infect bacteria. what they knew: -virus are composed of DNA and protein -virus infection reprograms a host cell to produce more virus. Question: which viral component is responsible for the reprogramming, DNA or protein. Bacteriophage/ Phage; Vir us that infects bacteria Radioactive sulfur which labels proteins Radioactive phosphorus which labels DNA virus injects DNA into host cell during infection, protein stays outside Dna provides info to reprogram host cells ti make more virus in virus, DNA is the hereditary material, not proteins. 1950-Mauric Wilkins and Rosalin franklin xray- crystallography: physics approach to examining biological molecules. ranklins xray photo indicated: 1. backbone of alternating phosphate and sugars 2. backbone is a helical structure 3. double helix structure(molecule is a uniform helix_ 4. Nitrogenous bases are in the middle of the molecuse 5. Bases are at right angels to the backbone they knew that each base could pair with partner, pyrimidine with purine. 1953-James Watson and francis crick Inspired by alpha-helix model of proteins discovered how A+T and G+C bonded together. Rosalin width of purine+pyrimidine bonds fit perfectly between the sugar-phosphate ackbone. the double helix model offer ed an easy method for replication. regular pattern typical of helical structure reminiscent of the alphahelix in proteins deterimingd rules of base pairing-size and hydrogen bonding Anti-parallel nature of strands. 1953- linus pauling proposed thr alpha helix seconday structure in proteins triple helix DNA model: 3 strands intertwined What was wrong: -phosphate groups were shown as neutral molecules -phosphates organized in the core for the helix-negative charges on oxygen would repel -Bases facing outwards.