dna replication

• in 1953, watson and crick the double helix structure was determined
• meselson and stahl found evidence for semi-conservative replication
• conservative or semi-conservative?

  .

  A) conservative

  
• conservative or semi-conservative?

  .

  A) semi-conservative

  
• dna bases are nitrogenous
• nitrogen has 2 isotopes 14N and 15N
• isotope


  different forms of an element that have the same number of protons but a different number of neutrons
• bacteria take in nitrogen isotopes to make new DNA nucleotides
• if you centrifuged 14N and 15 N bacteria would end up at different places in the tube
• why is dna replication an important process


  • when cells divide the daughter cells must receive an exact copy of the genetic material from the parent
  • in order for this to happen the DNA must be replicated or copied
• Process of DNA replication


  • DNA helicase unzips the 2 strands- the enzyme breaks the hydrogen bonds holding the base pairs together
  • Free nucleotides bind- complementary based pairing and each base acts as a template
  • DNA polymerase joins the new nucleotides together- dna polymerase joins new nucleotides forming the sugar-phosphate backbone
  • replication finished- 2 DNA molecules with one new synthesised strand of DNA and one strand of original. DNA is then rewound