Overview of DNA Replication
DNA replication is a semi-conservative process that occurs before cell division, allowing each daughter cell to receive an identical copy of the genetic material. It begins at specific sites called origins of replication, where the double helix unwinds, and new strands are synthesized using the original strands as templates. This ensures fidelity in genetic inheritance.
Key Steps and Enzymes Involved
The process involves several stages: initiation, where helicase unwinds the DNA and single-strand binding proteins stabilize the strands; elongation, where DNA polymerase adds nucleotides to the growing chain in a 5' to 3' direction, with leading and lagging strands formed differently; and termination, where ligase seals the Okazaki fragments on the lagging strand. Primase synthesizes RNA primers to start synthesis.
Practical Example: Replication in Prokaryotes
In bacterial cells like E. coli, replication starts at a single origin and proceeds bidirectionally around the circular chromosome. Helicase unwinds the DNA, forming a replication fork, and DNA polymerase III extends the new strands. This rapid process completes in about 40 minutes, producing two identical bacterial genomes for daughter cells.
Importance and Real-World Applications
Accurate DNA replication is essential for growth, repair, and reproduction in all living organisms, preventing mutations that could lead to diseases like cancer. Understanding this process aids in biotechnology, such as PCR for DNA amplification, and informs treatments for replication-related disorders.