Semi-conservative replication

• How does DNA replicate?

  By semi-conservative replication
• What does DNA do before cell division?

  Copies itself- so that each new cell has the full amount of DNA
• Why is it called semi-conservative replication?

  Half the strands in each new DNA molecule are from the original DNA molecule. this means there is genetic continuity between generations of cells
• First step of DNA replication?

  DNA Helicase breaks hydrogen bonds between bases on the 2 polynucleotide DNA strands - makes the helix unwind to form two single strands
• second step of DNA replication?

  Each original single strand acts as a template for a new strand.

  Complementary base pairing means that free-floating DNA nucleotides attracted to their complementary exposed bases on each original template strand (A+T, C+G)
• Third step of DNA replication?

  Condensation reactions join nucleotides of new strands together - catalysed by DNA POLYMERASE

  • Hydrogen bonds form between bases on original and new strands
• Fourth step of DNA replication
• Fourth step of DNA replication?

  Each new DNA molecule contains one strand from original DNA molecule and one new strand