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DNA Synthesis.pptx

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DNA replication involves unwinding the double helix at the replication fork using helicase. DNA polymerase then adds complementary nucleotides to each strand according to Watson and Crick's base pairing rules, forming two identical copies of the original DNA molecule. Meselson and Stahl's experiment showed that replication is semiconservative, with each new DNA molecule containing one original and one new strand. The leading strand is synthesized continuously towards the replication fork while the lagging strand involves discontinuous Okazaki fragments joined by DNA ligase.

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DNA Synthesis kHZ
DNA Replication Watson & Crick strands are complementary; nucleotides line up on template according to base pair rules (Watson) Meselson & Stahl replication is semiconservative; Expt: varying densities of radioactive nitrogen
DNA Replication: a closer look Origin of replication (bubbles): beginning of replication Replication fork: Y-shaped region where new strands of DNA are elongating Helicase: catalyzes the untwisting of the DNA at the replication fork DNA polymerase: catalyzes the elongation of new DNA
How replication occurs DNA replication is carried out by enzymes that unzip a molecule of DNA. Hydrogen bonds between base pairs are broken and the two strands of DNA unwind. The principal enzyme involved in DNA replication is DNA polymerase. DNA polymerase joins individual nucleotides to produce a DNA molecule and then proofreads each new DNA strand.
DNA Replication
DNA Replication Antiparallel nature: sugar/phosphate backbone runs in opposite directions (Crick) one strand runs 5 to 3, while the other runs 3 to 5; DNA polymerase only adds nucleotides at the free 3 end, forming new DNA strands in the 5 to 3 direction only
DNA Replication Leading strand: synthesis toward the replication fork (only in a 5 to 3 direction from the 3 to 5 master strand) Lagging strand: synthesis away from the replication fork (Okazaki fragments); joined by DNA ligase (must wait for 3 end to open; again in a 5 to 3 direction) Initiation: Primer (short RNA sequence~w/primase enzyme), begins the replication process

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DNA Synthesis.pptx

  • 2. DNA Replication Watson & Crick strands are complementary; nucleotides line up on template according to base pair rules (Watson) Meselson & Stahl replication is semiconservative; Expt: varying densities of radioactive nitrogen
  • 3. DNA Replication: a closer look Origin of replication (bubbles): beginning of replication Replication fork: Y-shaped region where new strands of DNA are elongating Helicase: catalyzes the untwisting of the DNA at the replication fork DNA polymerase: catalyzes the elongation of new DNA
  • 4. How replication occurs DNA replication is carried out by enzymes that unzip a molecule of DNA. Hydrogen bonds between base pairs are broken and the two strands of DNA unwind. The principal enzyme involved in DNA replication is DNA polymerase. DNA polymerase joins individual nucleotides to produce a DNA molecule and then proofreads each new DNA strand.
  • 6. DNA Replication Antiparallel nature: sugar/phosphate backbone runs in opposite directions (Crick) one strand runs 5 to 3, while the other runs 3 to 5; DNA polymerase only adds nucleotides at the free 3 end, forming new DNA strands in the 5 to 3 direction only
  • 7. DNA Replication Leading strand: synthesis toward the replication fork (only in a 5 to 3 direction from the 3 to 5 master strand) Lagging strand: synthesis away from the replication fork (Okazaki fragments); joined by DNA ligase (must wait for 3 end to open; again in a 5 to 3 direction) Initiation: Primer (short RNA sequence~w/primase enzyme), begins the replication process