AQA Biology Unit 2 Section 2 : Genetics

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DNA is made up of nucleotides that contain a sugar, phosphate and a base

  • DNA is a polynucleotide - many nucleotides
  • Each nucleotide is made from a pentose sugar, phosphate group and nitrogenous base
  • The sugar is a deoxyribose sugar
  • Each nucleotide has the same sugar and phosphate. the base on each nucleotide can vary though
  • These are A,T,C,G

Two polynucleotides join together to form a double helix

  • DNA nucleotides join together to form polynucleotide strands
  • This form the sugar-phosphate backbone
  • The two strands are joined by hydrogen bonds at the bases
  • Each base can only join with one particular partner - specific base pairing
  • The strands wind up to form a double helix

DNA's structure makes it good at its job

  • DNA contain genetic information - all the information needed to grow and develop
  • DNA can be coiled up tightly allowing it to fit into a small space in the cell nucleus
  • DNA molecules have a paired structure, which makes it much easier to copy itself. Self replication. This is important for passing information from generation to generation
  • The double helix means DNA is very…


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