北京大学：《微生物学》课程PPT教学课件（英文版）Chapter 5 Macromolecules and Molecular Genetics

Chapter 5 Macromolecules and Molecular Genetics DNA Replication Complementary base pairing Semiconservative Template and primer From 5-phosphate to the 3 -hydroxyl end dNa polymerase and ligase A short stretch of rna serves as a primer Primase: a specific RNA-polymerizing enzyme

Chapter 5 Macromolecules and Molecular Genetics DNA Replication Complementary base pairing Semiconservative Template and primer From 5’-phosphate to the 3’-hydroxyl end DNA polymerase and ligase A short stretch of RNA serves as a primer Primase: a specific RNA-polymerizing enzyme

Initiation of DNA synthesis 1. Origin of replication 300 bases with specific 2. DNA double helix opens up at the origin of replication Primase 3. Replication fork (left) 4. Bidirectional replication Single-stranded binding prot 5. Theta structure in DNA polymerase circular dna 6. Single eukaryotic 3 chromosome has many origins 7. Replication is carefully regulated 3

Initiation of DNA synthesis 1. Origin of replication: 300 bases with specific sequence; 2. DNA double helix opens up at the origin of replication 3. Replication fork (left) 4. Bidirectional replication 5.Theta structure in circular DNA 6. Single eukaryotic chromosome has many origins 7. Replication is carefully regulated

Ongin of DNA replication process 1. Leading strands: 5'-P3-OH 2. Lagging strands: 5-PRNA 3-OH Newly syn 3. DNA polymerase I,Il,III orks Ongin eac Leading Lagging Direchon Replication Replication fork

DNA replication process 1. Leading strands: 5’-P 3’-OH 2. Lagging strands: 5’-P RNA 3’-OH 3. DNA polymerase I, II, III

Leading and Lagging Strands Leading strand: DNa synthesis occurs continuously from the 5 -phosphate to the 3-hydroxyl Lagging strand: DNA synthesis occurs discontinuously Enzymes in lagging strand synthesis DNA primase, DNA polymerase III and I, DNA ligase

Leading and Lagging Strands Leading strand: DNA synthesis occurs continuously from the 5’-phosphate to the 3’-hydroxyl; Lagging strand: DNA synthesis occurs discontinuously. Enzymes in lagging strand synthesis: DNA primase, DNA polymerase III and I, DNA ligase

DNA polymerase Ill RNA pn 3-0H 5-P Kazak F raguel Single-stranded binding prote DNA polymerase I Heics DNA polymerase Free 3-OH Enzymes in lagging strand synthesis DNA primase 13 DNA polymerase III and I DNA ligase

Okazaki Fragment Enzymes in lagging strand synthesis: DNA primase, DNA polymerase III and I, DNA ligase

Proofreading: DNa polymease III has 325 exonuclease activity G A C丰G C主G G主C G主c Abnormal bonding Mismatched bonding nucleotide DNA polymerase ll 4. 3

Proofreading: DNA polymease III has 3’ 5’ exonuclease activity

nC DNA Replication of Linear Genetic Elements: Protein primer and Telomerase RNA tem lined to 5

Replication of Linear Genetic Elements:Protein Primer and Telomerase

Questions on DNA replication Describe the DNA replication process What proteins are involved in initiation of DNA synthesis Dna replication fork)? How do leading-and lagging strands replicate? What are enzymes involved in replicating the lagging strand? What are the differences between replicating circular dna and linear dna

Questions on DNA replication Describe the DNA replication process. What proteins are involved in initiation of DNA synthesis (DNA replication fork)? How do leading- and lagging strands replicate? What are enzymes involved in replicating the lagging strand? What are the differences between replicating circular DNA and linear DNA

RNA Structure and Function? RNA acts at two levels: Genetic and Functional Genetically: carry the genetic information from DNA Functionally: Structural role Messenger RNA (mRNA) RibosomaIrna (rrNa) Transfer RNA(tRNA) Catalytic RNA: Ribozyme

RNA Structure and Function? RNA acts at two levels: Genetic and Functional: Genetically: carry the genetic information from DNA; Functionally: Structural role • Messenger RNA (mRNA) • Ribosomal RNA (rRNA) • Transfer RNA (tRNA) • Catalytic RNA: Ribozyme

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