DNA and the Gene Synthesis and Repair

DNA and the Gene Synthesis and Repair - Chapter 14 DNA and...

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Chapter 14: DNA and the Gene I. What are Genes Made of? The chromosome theory of inheritance proposed that chromosomes are composed of genes. Chromosomes are a complex of DNA and proteins. a. The Hershey-Chase Experiment i. Hershey and Chase wonder whether genes are made of DNA or protein. They begin their study with E. Coli. They conclude that proteins contain sulfur but not phosphorus and DNA contains phosphorus but not sulfur. ii. They began growing viruses in the presence of either a radioactive isotope of sulfur, or phosphorus. Because these isotopes were incorporated into newly synthesized proteins and DNA, this step produced a population of viruses with radioactive proteins and a population with radioactive DNA. iii. If genes consist of DNA, then radioactive protein should be found only in the ghost capsids outside the infected host cells, while radioactive DNA should be located inside the cells. But if genes consist of proteins, then only radioactive protein should be found in the cells. iv. Virtually all of the radioactive protein was in the ghosts, while, virtually all of the radioactive DNA was in the host cell. v. DNA is the hereditary material. DNA contained all the information for life’s complexities. b.The Secondary Structure of DNA i. DNA is a long, linear polymer made up of monomers called deoxyribonucleotides, which consist of a deoxyribose molecule, a phosphate group, and a nitrogenous base. Deoxyribonucleotides link together into a polymer when a phospodiester bond forms between the hydroxyl group and the 3’ carbon of one of the deoxyribose and the phosphate group attached to the 5’ carbon of another deoxyribose. ii. A DNA molecule has two major components (1) a “backbone” made up of the sugar and phosphate groups of deoxyribonucleotides and (2) a series of nitrogen-containing bases that project from the backbone. A strand of DNA has a directionality or polarity: one end has an exposed hydroxyl group on 3’ carbon of a deoxyribose, while the other has an exposed phosphate group on a 5’ carbon. iii.
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This note was uploaded on 03/16/2011 for the course BIO 180 taught by Professor Chamberlain during the Spring '08 term at Staten Island.

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DNA and the Gene Synthesis and Repair - Chapter 14 DNA and...

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