DNA basics

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  • Created by: Tom
  • Created on: 08-05-13 20:02

what makes DNA

  • DNA is a polynucleotide - its made up of lots of nucleotides joined together
  • each nucleotide is made from a pentose sugar (with 5 carbon atoms) a phosphate group and a nitrogen base
  • the sugar in DNA nucleotides is a deoxyribose sugar
  • each nucleotide has the same sugar and phosphate. the base on each nucleotide can vary through.
  • there are four possible bases - adenine (A), thymine (T), cystosine (C) and Guanine (G)

(http://alevelnotes.com/content_images/i11_nucleotide1.jpg)

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what forms a double helix

  • DNA nucleotides join together to form poly-nucleotide strands
  • the nucleotide join up between the phosphate group of one nucleotide and the sugar of another, creating a sugar-phosphate backbone
  • two DNA polynucleotide strands join together by hydrogen bonds between bases
  • each base can only join with one particular partner - this is called specific base pairing
  • adenine always pairs with thymine (A - T) and guanine always pairs with cytosine (G - C)
  • the two strands wind up to form the DNA double-helix
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