Dna

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Dna

  1. 1. DNA
  2. 2. DNA is a nucleic acid• A nucleic acid is a polymer of nucleotides• A nucleotide is made from a phosphate, sugar and base.• www.chemsoc.org
  3. 3. Phosphate• From phosphoric acid• http://bio.winona.edu/berg/ChemStructures/Phospha2.gif
  4. 4. Sugar• Deoxyribose in DNA (Ribose in RNA)• http://www.mun.ca/biology/scarr/Deoxyribose_vs_Ribose.gif
  5. 5. Nucleotide• Condensation between the phosphate and sugar (at C5) and between the sugar (at C1) and base• http://distancelearning.ksi.edu/demo/bio378/DNA_files/image002.gif
  6. 6. Dinucleotide• Two nucelotides join by condensation• http://pages.towson.edu/jdrawn/Chapter_1_Intro_to_Bioinfo_files/image005.jpg• Condensation gives phosphodiester bridge
  7. 7. Polynucleotide• Up to 5 x 106 nucleotides long• http://seqcore.brcf.med.umich.edu/doc/educ/dnapr/oligo.gif• 5’ end• 3’ end
  8. 8. DNA double helix• The bases of the DNA nucleic acid form H bonds to bases of a second molecule of DNA
  9. 9. • A bonds to T with two hydrogen bonds• G bonds to C with three hydrogen bonds.• http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/BasePairing.gif
  10. 10. • A is the ~same amount as T• G is the ~same amount as C• Amount of purines equals the amount of pyrimidines• A always bonds to T• G always bonds to C• Known as Chargaff’s Rule
  11. 11. Table from Biological Science – Green, Stout, Taylor
  12. 12. • The two nucleic acids wind into a double helix, with H bonds between polar groups of sugars keeping the shape of the helix.• (diagram from Bioligical Sciences, green, Stout & Taylor)
  13. 13. • The two strands are ANTIPARALLEL• i.e. they are parallel, but run in opposite directions.
  14. 14. http://www.accessexcellence.org/RC/VL/GG/images/dna2.gif
  15. 15. Arrangement of DNA in chromosomeshttp://www.biology.emory.edu/research/Lucchesi/multimedia/images/insert2.jpg
  16. 16. Histones in nucleosome• DNA is wrapped around a group of 8 histone proteins and held together by another histone molecule• http://employees.csbsju.edu/hjakubowski/classes/ch331/dna/nucleosome.gif
  17. 17. • Nucleosomes:• Help in supercoiling of DNA• Help to regulate transcription
  18. 18. DNA from a single skin cell, ifstraightened out, would be about six feet long but invisible. Half a gram of DNA, uncoiled, would stretch to the sun. Again, you couldnt see it.

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