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Published byJade Chapman Modified over 9 years ago
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DNA is the only molecule that is capable of replicating itself DNA provides for the continuity of life and accounts for the biodiversity of all life forms
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In 1943 Joachim Hammerling found that the nucleus in the cell was the likely “holder” of hereditary information He used a large single-celled green algae Acetabulaira which grows up to 5 cm
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When he cut the algae in distinct pieces, only the rhizoid (foot) was capable of growing a new stalk and cap – it held the nucleus
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Regardless of what stem was put on the foot, it was the identity of the foot that would cause the specific cap to grow (they “matched”)
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Work with a partner or on your own and do the investigation on page 644 and 645. Hand in one page per group
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Frederick Griffith, Avery, McCarty and MacLeod did work that questioned the assumption that protein was the heritable material
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Hershey and Chase used a virus or a bacteriophage T2 which affects its bacterial host The phage is composed of 2 parts 1) Protein coat 2) DNA
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The virus survives and duplicates by attaching to the bacteria and injecting its hereditary into it The bacteria begins to make the new viruses inside it and it eventually bursts with thousands of viruses coming out http://www.youtube.com/watch?v=41a qxcxsX2w&feature=related http://www.youtube.com/watch?v=41a qxcxsX2w&feature=related
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Hershey and Chase proved that DNA was the hereditary material by using tagged viral proteins with a radioisotope of sulphur and phosphorus Both of the radioisotopes give off radiation as they decay Sulphur is found in the protein coat while phosphorus is found in the DNA
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What molecule would you expect to be found inside the bacteria? The radioactive phosphorus was found within the bacteria The radioactive sulphur was found outside of the bacteria DNA was accepted as the hereditary material Check out the diagram on page 647
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James Watson and Francis Crick discovered the structure of DNA with the help of a picture (X-ray diffraction) taken by Rosalind Franklin
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Nucleotide – molecule having a five- carbon sugar with a nitrogenous base attached to its 1’ carbon and a phosphate group attached to its 5’ carbon Nitrogenous base – an alkaline cyclic molecule containing nitrogen
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Deoxyribose sugar – a sugar molecule containing five carbons that lost the –OH (hydroxyl group) on its 2’ position Phosphate group – a group of four oxygen atoms surrounding a central phosphorus atom found in the backbone of DNA
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DNA is made up of 3 things 1) Phosphate group – makes up the “edges” of the ladder – same for each 2) Deoxyribose sugar (made up of 6 carbons, 5 within a ring) – same for each
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3) Nitrogen base – there are 4 and all contain nitrogen – causes the difference ADENINE, GUANINE, CYTOSINE, THYMINE Note: the amount of adenine always equals the amount of thymine and the amount of guanine always equals the amount of cytosine
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Read page 650 as a class on Politics and Science Page 657 #1-10, 17-20, 22-24
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