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8. Nucleotides and Nucleic Acids

8. Nucleotides and Nucleic Acids. Chapter 8 Lehninger 5 th ed. Nucleotides. “Energy rich” compounds Chemical signals Enzyme co-factors Nucleic Acids DNA and RNA Polymers of nucleotides 3 components Nitrogenous “base” Ribose (or deoxyribose) Phosphate. “Bases”. 2 p urine bases

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8. Nucleotides and Nucleic Acids

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  1. 8. Nucleotides and Nucleic Acids Chapter 8 Lehninger 5th ed.

  2. Nucleotides • “Energy rich” compounds • Chemical signals • Enzyme co-factors • Nucleic Acids • DNA and RNA • Polymers of nucleotides • 3 components • Nitrogenous “base” • Ribose (or deoxyribose) • Phosphate

  3. “Bases” • 2 purine bases • Adenine: A • Guanine: G A G • Bases • Pyrimidines • Purines C T U • 2 pyrimidine bases (in DNA) • Cytosine: C • Thymine: T • orUracil: U • (in RNA, instead of Thymine)

  4. 5’ 1’ 4’ 3’ 2’ Ribose • carbons numbered: • 1’,2’,3’,4’,5’ • DNA: • 2’ Deoxyribose • or just deoxyribose

  5. Nucleotides SummaryDNA A,C,G,T deoxyriboseRNA A,C,G,U ribose

  6. Polymerise Nucleotides • nucleotides can be linked • phosphates linked to 2 pentoses • phosphodiester linkages • Link PO4 at • 5’ end to 3’ OH of next nucleotide • chain has POLARITY • distinct ends • 5’ end • 3’ end • usually “read” 5’ -> 3’

  7. Nucleotides as Energy Carriers • ATP • Adenosine triphosphate • ADP, AMP • Adenosine diphosphate • Adenosine monophosphate • ATP <--> ADP + PO4 • ADP <--> AMP + PO4 • Main energy exchange reactions in cells

  8. Structure of DNA? • The Genetic Material • Crick and Watson • Race with Linus Pauling to predict structure • Chargaff’s rules: • Chemical analysis: [A] = [T] [G] = [C] • Constant • for each organism • over time • across all tissues

  9. X-Ray Diffraction • Predict • Double helix • 2 periodicities • 3.4Å • 34Å

  10. Base Pairing • A – T basepair • 2 h-bonds • G – C basepair • 3 h-bonds • 2 anti-parallelDNA strands

  11. The Double Helix • 3.4Å per basepair • 10 basepairs per turn • 10-11 in aqueous solution • 2 anti-parallel strands

  12. DNA Replication • By DNA Polymerase

  13. RNA • Usually single stranded • Genetic material of RNA virus • Functional: • e.g. Translation machinery • rRNA (ribosomal RNA) • tRNA (transfer RNA) • Regulatory: • Control of gene expression • miRNA (microRNA) • Gene Expression • mRNA (messenger RNA) • Copy of 1 gene for translation by ribosomes

  14. RNA Secondary Structure • RNA single stranded • Can form base pairs internally

  15. RNA Secondary Structure • Many functional RNAs have secondary structure • G-U basepairs allowed

  16. DNA Sequencing

  17. DNA Sequencing

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