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bio exam 3 study questions - IV DNA(CFH Objectives 1 Draw...

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IV. DNA (CFH) Objectives 1. Draw and define the components of a nucleotide. Know the difference between guanine, cytosine, adenine, and thymine. Nucleotides are composed of the same phosphate group, one of two 5-carbon sugars (ribose or deoxy ribose), and one of five nitrogen and carbon containing ring structure called a nitrogenous base. The difference between guanine, cytosine, adenine, and thymine is in the number of rings, the number of nitrogens, and functional groups. 2. Distinguish between purines and pyrimdines. Uracil (U) is also a pyrimidine for RNA that replaces Thymine in DNA 3. Draw and describe the structure of DNA. The structure of DNA is an alpha-helix (resembles a twisting ladder). It has a phosphate and sugar backbone with the nitrogenous bases pairing to be the rungs of the ladder.
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4. Draw and name the chemical bond that connects nucleotides in a DNA strand. Phosphodiester bonds are the chemical bonds that connect nucleotides in a DNA strand. The phosphate group on the 5’ carbon of one sugar bonds to the 3’ carbon of another sugar. 5. Draw and describe the bonds that hold together two DNA strands. Hydrogen bonds (covalent bonds) are the chemical bonds that hold together two DNA strands. Guanine and Cytosine bond to each other with 3 hydrogen bonds while Adenine and Thymine bond to each other with only 2. 6. Explain complementary base pairing (Watson-Crick pairing). Describe how base pairing enables DNA replication. Complimentary base pairing is the fact that Adenine pairs with Thymine (Uracil in RNA) and Guanine pairs with Cytosine. It enables DNA replication because a single strand of DNA can serve as a template and can be “read” to give a new, semi-conservative double strand of DNA. Gives the ability to duplicate genetic information. 7. Explain the function of DNA. Describe the experiments that lead to the discovery of DNA as hereditary material. DNA contains all the genetic information of an organism. Hershey and Chase found that Radioactive DNA was found in phage infected bacteria. Avery, MacLeod and McCartey found that only the DNA fraction of virulent pneumococcus cells was capable of transforming non-virulent pneumococcus cells. Griffith found that non-virulent pneumococci can be transformed into virulent pneumococci by incubating with heat- killed virulent pneumococci. Avery alone found that variations in virulence of pneumococci were dependent on coat polysaccharides.
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8. Describe the experiment performed by Matthew Meselson and Frank Stahl. Meselson and Stahl used heavier isotopes of nitrogen in DNA replication. After the first generation they knew DNA was not conservative; it was conservative or dispersive. After the second generation they knew it was semi-conservative and it was not dispersive.
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