Lecture Notes: DNA Replication

Introduction to DNA and Its Importance

• DNA is the ultimate director for cells, coding for traits.
• During cell division, new cells require DNA replication to provide each daughter cell with DNA.

Where and When DNA Replication Occurs

• Where:
  • In eukaryotic cells, replication occurs in the nucleus.
  • Prokaryotic cells also perform DNA replication but lack a nucleus.
• When:
  • DNA replication occurs before cell division, specifically during interphase in eukaryotic cells.

Key Enzymes in DNA Replication

• Helicase:
  • Unzips the DNA strands by breaking hydrogen bonds.
• DNA Polymerase:
  • Replicates DNA molecules to build new strands.
• Primase:
  • Initializes the process by creating RNA primers.
• Ligase:
  • Glues DNA fragments together.

DNA Replication Process Overview

• Origin of Replication:
  • Helicase unwinds DNA at specific sequences.
• SSB Proteins:
  • Keep DNA strands separated.
• Topoisomerase:
  • Prevents DNA supercoiling during replication.
• Primase:
  • Creates RNA primers for DNA polymerase.
• Directionality of DNA Strands:
  • DNA strands are anti-parallel: 5' to 3' and 3' to 5'.
  • DNA polymerase builds new strands in the 5' to 3' direction.

Leading and Lagging Strands

• Leading Strand:
  • Built continuously in the 5' to 3' direction.
• Lagging Strand:
  • Built discontinuously in Okazaki fragments that are later joined by ligase.

Final Product and Proofreading

• Two identical double helix DNA molecules are produced, each with one original and one new strand (semi-conservative replication).
• DNA polymerase has proofreading capabilities to minimize errors.

Further Exploration

• Detailed understanding of DNA replication has led to medical advances.
• Explore further reading for more in-depth information.

Remember to stay curious and explore more about DNA replication and its implications in biology and medicine!