DNA Replication Lecture Notes

Overview

DNA is the ultimate director for cells, coding for traits.
During cell division, DNA replication is essential to pass DNA to daughter cells.

Definition: Making more DNA.
Location:
- Eukaryotic cells: Occurs in the nucleus.
- Prokaryotic cells: No nucleus, but DNA replication still occurs.
Timing:
- Occurs before cell division (mitosis or meiosis) during interphase.

Helicase: "Unzipping enzyme" that unwinds DNA by breaking hydrogen bonds between bases.
DNA Polymerase: "Builder enzyme" that replicates DNA strands, building new DNA.
Primase: "Initializer enzyme" that places RNA primers to guide DNA polymerase.
Ligase: "Gluer enzyme" that joins DNA fragments together.
SSB Proteins: Keep DNA strands separated during replication.
Topoisomerase: Manages DNA supercoiling.

Origin: Specific DNA sequences initiate replication.
Unwinding:
- Helicase unwinds the DNA.
- SSB proteins stabilize unwound strands.
- Topoisomerase prevents supercoiling.
Primer Placing:
- Primase places RNA primers on both strands.
Strand Construction:
- DNA polymerase builds new DNA strands in 5' to 3' direction.
Strand Types:
- Leading Strand: Built continuously.
- Lagging Strand: Built in Okazaki fragments; primers continually placed.
Final Steps:
- RNA primers replaced with DNA bases.
- Ligase seals gaps in Okazaki fragments.

Anti-parallel Strands: DNA strands run in opposite directions (5' to 3' and 3' to 5').
Base Pairing: Adenine pairs with Thymine; Guanine pairs with Cytosine.

Semi-Conservative Replication: Each new DNA molecule contains one original and one new strand.
Proofreading: DNA polymerase checks errors to prevent mutations.

Understanding DNA replication aids in developing medical treatments to inhibit harmful cell replication.

DNA replication is a complex, highly regulated process, crucial for genetic fidelity during cell division.
Encouragement to explore further and stay curious, as noted by the Amoeba Sisters.