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3.3 and 7.1 The structure of DNA

3.3 and 7.1 The structure of DNA. Deoxyribonucleic acid. DNA is a nucleic acid. A nucleic acid is a polymer of nucleotides 3.3.1- A nucleotide is made from three parts phosphate, sugar and base. Phosphate. From phosphoric acid http://bio.winona.edu/berg/ChemStructures/Phospha2.gif. Sugar.

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3.3 and 7.1 The structure of DNA

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  1. 3.3 and 7.1 The structure of DNA Deoxyribonucleic acid

  2. DNA is a nucleic acid • A nucleic acid is a polymer of nucleotides • 3.3.1- A nucleotide is made from three parts phosphate, sugar and base.

  3. Phosphate • From phosphoric acid • http://bio.winona.edu/berg/ChemStructures/Phospha2.gif

  4. Sugar • Deoxyribose in DNA (Ribose in RNA) • http://www.mun.ca/biology/scarr/Deoxyribose_vs_Ribose.gif

  5. 3.3.2- state the names of the four bases

  6. 7.1.1 Purines (have two rings) • http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/notes/chpt14/purine.gif

  7. 7.1.1 Pyrimidines (have one ring)*notice that the words pyrimidine, cytosine, and thymine all have the letter “y” in them (a way to remember )

  8. 3.2.5 formation of DNA from Nucleotides • Condensation between an oxygen on the phosphate connected to C5 and the OH group connected to C3 When the O from one nucleotide reacts with the OH from another nucleotide, it will form water

  9. Dinucleotide • Two nucleotides join by condensation • Condensation gives phosphodiester bridge

  10. 3.3.3 Outline how DNA nucleotides are linked together by covalent bonds into a single strand. • 5’ end • 3’ end

  11. DNA double helix • The bases of one strand of DNA form Hydrogen bonds to bases of a second strand of DNA

  12. Table from Biological Science – Green, Stout, Taylor

  13. 3.3.4 • A is present in the same amount as T • G is present in the same amount as C • Amount of purines equals the amount of pyrimidines • A always bonds to T • G always bonds to C

  14. 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

  15. The two strands of DNA wind into a double helix. • The double helix is made of two sugar-phosphate “backbones”, with the bases connecting them together with hydrogen bonds

  16. 7.1.1- DNA has 3’ to 5’ linkages and it’s two strands are antiparallel 5’ 3’ 5’ 3’

  17. 7.1.1 • The two strands are ANTIPARALLEL • i.e. they are parallel, but run in opposite directions (DNA has directionality due to its 3’ and 5’ ends).

  18. 7.1.2 Arrangement of DNA in nucleosomes http://www.biology.emory.edu/research/Lucchesi/multimedia/images/insert2.jpg

  19. Nucleosomes are made of histone proteins and DNA • DNA is wrapped around a group of 8 histone proteins and held together by another histone molecule

  20. 7.1.3 • Nucleosomes: • Help in supercoiling of DNA • When DNA is tightly coiled, called heterochromatic, the DNA is inactive • This prevents transcription, thus nucleosomes are involved in the regulation of transcription (making RNA, which leads to making protein)

  21. 7.1.4 Distinguish between unique or single-copy genes and highly repetitive sequencesin nuclear DNA. • A single copy gene is a segment of DNA that codes for a polypeptide chain and is generally unique from other parts of the genome • A repetitive sequence is a segment of DNA that repeats a short sequence over and over (I.e. ATCGATCGATCGATCG) • These sequences are also known as satellite DNA or junk DNA because it serves no purpose (as far as we know)

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