DNA Replication Lecture Notes

Introduction to DNA

DNA is the ultimate director for cells, coding for traits.
DNA replication is necessary for cell division to ensure daughter cells receive a copy of DNA.

Eukaryotic Cells: Occurs in the nucleus during interphase, before mitosis or meiosis.
Prokaryotic Cells: No nucleus, but still perform DNA replication.

Helicase: Unzips DNA strands by breaking hydrogen bonds.
DNA Polymerase: Builds new DNA strands by replicating DNA molecules.
Primase: Initializes the process by creating RNA primers for DNA polymerase to start.
Ligase: Glues DNA fragments together.

Origin of Replication
- Begins at specific DNA sequences identified as origins.
Unwinding DNA
- Helicase unwinds the DNA.
- SSB Proteins: Keep strands separated.
- Topoisomerase: Prevents supercoiling, which could interfere with the process.
Initiation by Primase
- Primase creates RNA primers on both DNA strands for DNA polymerase.
DNA Polymerase Function
- Directionality: DNA strands are anti-parallel; DNA polymerase builds in a 5’ to 3’ direction.
- Leading Strand: Continuous synthesis.
- Lagging Strand: Discontinuous synthesis, resulting in Okazaki fragments.
Okazaki Fragments
- RNA primers are replaced with DNA bases.
- Ligase seals the gaps between fragments.
Completion of Replication
- Results in two identical double helix DNA molecules.
- Semi-conservative method: Each DNA molecule contains one original and one new strand.

DNA Polymerase has proofreading ability to minimize errors.
Incorrect base pairing can lead to incorrect gene expression or protein formation.
Understanding of DNA replication has led to medical advancements in treating diseases.

DNA replication is a complex yet fundamental process in biology.
Encouragement to explore more details due to its significance in medical treatments and cellular biology.

Note: Further reading and exploration beyond the basics are encouraged for a more detailed understanding of the process.