DNA Replication Lecture Notes

Introduction to DNA

• DNA: ultimate director for cells, codes for traits
• Essential in cell division to pass DNA to daughter cells

DNA Replication Overview

• Definition: Making more DNA
• Where?
  • Eukaryotic cells: Nucleus
  • Prokaryotic cells: No nucleus, still perform replication
• When?
  • Before cell division (mitosis/meiosis)
  • During interphase in eukaryotic cells

Key Players in DNA Replication

1. Helicase: Unzipping enzyme, separates DNA strands by breaking hydrogen bonds.
2. DNA Polymerase: Builder enzyme, replicates DNA to build new strands.
3. Primase: Initializer enzyme, creates RNA primers to guide DNA polymerase.
4. Ligase: Gluer enzyme, joins DNA fragments together.

DNA Replication Process

• Starts at: Specific DNA sequence called the origin
• Key Steps:
  • Helicase unwinds DNA strands
  • SSB Proteins bind to keep strands separated
  • Topoisomerase prevents supercoiling
  • Primase places RNA primers on both strands
  • DNA Polymerase builds new strands in 5' to 3' direction
  • Leading Strand: Continuously built strand
  • Lagging Strand: Built in segments called Okazaki fragments
  • Ligase seals gaps between Okazaki fragments

DNA Structure

• Complementary Bases: Adenine pairs with Thymine, Guanine pairs with Cytosine
• Anti-parallel Strands: Directions are 5' to 3' and 3' to 5'

DNA Replication Outcomes

• Results in two identical double helix DNA molecules
• Known as semi-conservative replication

Quality Control

• Proofreading by DNA Polymerase: Rarely makes errors, ensures correct base pairing

Applications and Further Study

• Understanding DNA replication has led to medical advancements
• Explore more details for deeper understanding, including pathogenic and cancer treatment
• Encouragement to stay curious and explore further readings