Lecture on DNA Replication

Introduction

• DNA: The ultimate manager of cells and encodes genetic traits
• DNA Replication: The process of producing more DNA
• Importance of the process: Essential for cell division to form new cells containing the same genes

Where and When DNA Replication Occurs

• Where?:
  • In Eukaryotic cells: Occurs in the nucleus
  • In Prokaryotic cells: Occurs in the cytoplasm
• When?: Before cell division during the interphase (before mitosis or meiosis)

Key Players in DNA Replication

• Main Enzymes:
  • Helicase: Separates the DNA strands
  • DNA Polymerase: Replicates DNA to build a new strand
  • Primase: Makes an RNA primer to allow DNA Polymerase to start
  • Ligase: Connects DNA fragments together
• SSB Proteins: Maintain strand separation
• Topoisomerase: Prevents excessive DNA twisting

DNA Replication Process

1. Initiation at Origin:
   • Determined by a specific sequence
   • Helicase separates the strands
   • SSB proteins prevent re-annealing
   • Topoisomerase regulates DNA twisting
2. Primer Placement:
   • Primase makes an RNA primer
3. Building New Strands:
   • DNA Polymerase builds the new strand in the 5’ to 3’ direction
   • New strands are complementary and antiparallel
4. Leading and Lagging Strand:
   • Leading Strand: Built continuously
   • Lagging Strand: Built in fragments (Okazaki fragments)
5. Primer Removal and Fragment Joining:
   • Ligase joins Okazaki fragments

Semiconservative Nature of DNA Replication

• Two new cells obtain one old strand and one new strand

Error Correction

• DNA Polymerase corrects mistakes to ensure the accuracy of the process

Application of Understanding in Medical Treatments

• Stopping DNA replication in harmful cells such as pathogenic bacteria or cancer cells

Additional Reading Sources

• Check video notes and broader reading suggestions to discover more

Conclusion

• Exploring the details of DNA replication can lead to deeper understanding and new therapeutic experiments