DNA

DNA replication

• 1.       Helicase unwinds and separates the parental strand
• 2.       Another enzyme relieves the strain created by cutting the DNA creating a temporary break
• 3.       Free DNA mononucleotides join onto both strands by complementary base pairing, DNA polymerase adds these to the strand.
• 4.       DNA ligase joins the mononucleotides by creating phosphodiester bonds between them
• 5.       On one strand this is constant and the other creates okazaki fragments which are later joined together

Proof of DNA semi-conservative replication

• Bacteria grown in heavy ¹⁵N
• Some bacteria are transferred into light ¹⁴N and bacteria continue to grow
• A sample is taken after 20 minutes after one replication and 40 minutes after two replications
• Samples of extracted DNA is placed in test tubes
• The first accumulated at the bottom, the second in the middle and the third in the…