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Micro 02-20-08 - Whitney Barter 1 Chapter 8 R 1-4 6 8 11 14...

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Whitney Barter Chapter 8 – R 1-4, 6, 8, 11, 14, 15 2/20/08 1. Briefly describe the components of DNA, and explain its functional relationship to RNA and protein. DNA is a macromolecule composed of alternating units of deoxyribose (sugar) and phosphate groups. Each sugar is attached to a nitrogenous base: Adenine, Thymine, Cytosine and Guanine. DNA within a cell exists as long strands of nucleotides twisted together into pairs, A- T and C-G, forming a double helix. Much of cellular metabolism is concerned with translating the genetic message of genes into specific proteins. A gene usually codes for a messenger RNA (mRNA) molecule, which the final product is the formation of a protein. This is called gene expression. 2. Draw a diagram showing a portion of a chromosome undergoing replication. a. b. What is the role of DNA polymerase? Of RNA polymerase? DNA Polymerase During replication the double helix strands are unwound one segment at a time. Free nucleotides are then matched up appropriately (A-T or C-G). Once they are aligned DNA polymerase (an enzyme) adds the nucleotide to the growing DNA strand. Then the next segment is unwound. It will also make sure that the pairing is correct and if is not it will kick out the new nucleotides and replace it with the correct one. RNA Polymerase During transcription (the synthesis of a complementary strand of mRNA from a DNA template) RNA polymerase binds to the DNA at a site called the promoter. RNA polymerase will then assemble free nucleotides into a complementary chain of DNA. As the new RNA is formed the RNA polymerase moves does the chain. RNA synthesis will continue until the RNA polymerase reaches a site of the DNA called the terminator. Then the RNA polymerase and the new single-strand RNA are released from the DNA. a. How does this process represent semi-conservative replication? This process represents semi-conservative replication because each new double stranded DNA molecule contains one original (conserved) strand and one new strand.
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3. The following is a code for a strand of DNA.
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