DNA Replication

 
DNA
must replicate itself to ensure that an exact copy of the species genetic information is passsed from cell to cell during growth. It does this in several stages.
 
  1. The double helix structure of DNA unwinds.
  2. Weak hydrogen bonds between two adjacent bases break and causing the two DNA strands to seperate or "unzip" and expose their bases.
  3. Free DNA nucleotides find and align with there complementary bases on the "open" strand.
  4. Weak hydrogen bonds form between two complementary bases that have "matched".
  5. Strong chemical bonds form betweem the sugar of one free nucleotide and the phosphate of the next one in the chain giving each strand its sugar-phospate backbone. this linking of nucleatides is controlled by an enzyme called DNA Polymerase
  6. The two new daughter strands of DNA coil up. these two strands have a base sequence identical to each other and to the original DNA molecule so therefore will code for the same proteins
 

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After DNA replication the two identical daughter DNA molecules formed coil up and become two identical chromatids held together by a centromere. Therefore the quantity of genetic material has doubled withour changing the cells chromosomes number.
 
For DNA replication to occur the nucleus must have:
 
  • DNA
  • A supply of the four types of DNA nucleotide
  • Appropriate enzymes
  • ATP to provide energy
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