biol1201 final study guide part b

biol1201 final study guide part b - *In comparison to RNA,...

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*In comparison to RNA, DNA lacks a 2’ hydroxyl group *the double helix is anti-parallel. This refers to the directionality of the two strands True *the base pairing between strands is stabilized by hydrogen bonds. * “A” pairs with what base? T Figure 16.7, 16.8 pg. 298- unnumbered figure Base Pairing - Suggest a model for DNA replication o How do you make identical copies? Figure 16.9 Semi-conservative replication - Each strand of the original double helix serves as a template for a new complementary strand - Mendelson and Stahl experiment - Figure 16.10, 16.11,16.12, 16.13 When is DNA replicated? S phase DNA synthesis - Polymer synthesized from monomers o DNA polymerase - Polymer grows by adding a new nucleotide triphosphate to the 3’ – OH group of the growing DNA strand - Covalent bond formed involving the 5’ phosphate and the 3’ hydroxyl - 16.13 Treatment of HIV/AIDS with AZT - Block the production of viral DNA AZT - 3’ azido (N₃) group instead of 3’ OH group - When AZT is added to growing viral DNA strand the azido group stops the addition of further nucleotides - The azido group cannot form a covalent bond with a 5’ phosphate Human DNA does not incorporate AZT. Why? Proof reading ability of DNA polymerase compared to the viral reverse transcriptase DNA Synthesis - Single stranded DNA serves as a template for the new strand - DNA synthesis is “primed” with a short segment of RNA synthesized by the enzyme primase - DNA elongation catalyzed by enzyme DNA polymerase - RNA primer is replaced by DNA synthesized by DNA polymerase DNA polymerase - Only works in the 5’ to 3’ direction o Adds new nucleotide to the 3’ OH of the growing chain - Proof- reading abilities *the enzyme that inserts the RNA primer in DNA synthesis. Primase DNA polymerase works 5’ to 3’ I.e. adds nucleotides to the 3’ hydroxyl leading and lagging strands - problem of DNA synthesis with anti- parallel double strands Figure 16.14 Double stranded DNA synthesis - Leading strand synthesized 5’ to 3’ in the direction of the replication fork
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- Lagging strand synthesized 5’ to 3’ away from the replication fork - Okazaki fragments - Okazaki fragments linked together by enzyme ligase 16.18, 16.1 * both leading and lagging strands are synthesized 5’ to 3’ * stitches together Okazaki fragments. Ligase 9/04/07 Quiz 27 due Wednesday Molecular genetics worksheet- blackboard documents *the enzyme that inserts the RNA primer in DNA synthesis Primase *stitches together Okazaki fragments Ligase *both the leading and lagging strands are synthesized 5’ to 3’ Table 16.1, figures 16.18, 16.17 Actually - A single DNA polymerase complex forms both the leading and lagging strands DNA Damage - Thymine dimer formation by ultraviolet light The ends of chromosomes figure 16.19 - Problem of adding nucleotides only in the 5’ to 3’ direction at the end of a strand of DNA where there is no 3’ OH group to bond with. Telomerase
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This note was uploaded on 04/10/2008 for the course BIOL 1201 taught by Professor Wishtichusen during the Spring '07 term at LSU.

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biol1201 final study guide part b - *In comparison to RNA,...

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