🔬 DNA Replication Simulation
Observe the unwinding of a double helix and synthesis of new DNA strands.
🔬 DNA Replication Stages
1. Unfolding the spiral
DNA helicase unwinds the double helix of DNA, breaking hydrogen bonds between complementary nucleotides. This creates a replication fork - Y-shaped structure.
2. Stabilizing chains
Proteins that bind single-stranded DNA (SSB) attach to unwound strands, preventing their rejoining and protecting from enzymes that break DNA.
3. Synthesizing a primer
DNA primase synthesizes a short RNA primer (10-12 nucleotides) that serves as the starting point for DNA polymerase. The primer is complementary to the template strand.
4. Stretch of the chain
DNA polymerase adds nucleotides to the 3'-end of the primer, following the principle of complementarity: A with T, G with C. Synthesis occurs in the 5'→3' direction.
🧬 Replication Features
Semi-conservative process
Each daughter DNA molecule contains one maternal strand and one newly synthesized. This ensures accurate copying of genetic information and its transmission to the next generation.
Bidirectionality
Replication starts at multiple points simultaneously and proceeds in both directions. This significantly speeds up the copying process for large DNA molecules.
Leading and lagging chains
On the leading strand synthesis occurs continuously in the direction of the replication fork. On the lagging strand synthesis occurs in fragments (Okazaki fragments).
Error correction
DNA polymerase has exonuclease activity, allowing it to correct errors during synthesis. Additional repair systems correct any remaining errors.
❓ Frequently Asked Questions
In bacteria, replication takes about 40 minutes. In humans, replicating all DNA (6 billion base pairs) takes 6-8 hours. The process occurs simultaneously at many points, speeding it up.
Telomeres are repeated DNA sequences at the ends of chromosomes. They shorten with each replication, which is linked to cellular aging. Telomerases can restore telomeres in stem cells and cancer cells.
YES, errors occur with a frequency of 1 in 10 million nucleotides. Most are corrected by repair systems. Unrepaired errors can lead to mutations that sometimes benefit evolution.
S-phase (synthetic phase) is a period of the cell cycle when DNA replication occurs. This ensures that daughter cells receive a complete set of genetic information before division.
Replication fork - a Y-shaped structure that forms during DNA unwinding. Here new chains are synthesized. It contains replication enzymes and moves along the DNA molecule.