Biochem 501: Part IV.2: Nucleic Acid Chemistry and Chromosome Structure

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Anonymous
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251099
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Biochem 501: Part IV.2: Nucleic Acid Chemistry and Chromosome Structure
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2013-12-05 19:34:11
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Biochem 501 FINAL
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Biochem 501 FINAL
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  1. Which is more stable, DNA or RNA?
    • DNA
    • RNA is prone to hydrolysis, resulting in breaking off of nucleotides at the phosphodiester bond
  2. What can cause a DS to become a SS
    Heat or solutions conditions such as pH
  3. When heat is added to a DS DNA why does it only split into 2 stands
    Strands held together by hydrogen bonds which are broke, Strand itself is held together by stronger covalent bonds
  4. DNA melting temperature effected by:
    • Nonpolar solvents (disrupt base stacking)
    • Cations (Shield phosphate charges)
    • pH
    • mismatches (destabilize DS form)
  5. DNA denaturement and gene expression
    • Denaturement occurs at start of gene before expression
    • Lower Tm facilitate denaturement
    • Denaturement needed so transcription machinery can access DNA
    • DNA denatured during genome replication
  6. How does DNA compact?
    Super-coiling
  7. What does super-coiling compensate for?
    Structural strain from unraveling DNA
  8. Topological Properties
    • Properties that are unchanged by deformation (such as super-coiling)
    • Can only be changed by cleaving and rejoining strands.
  9. What carries out topological changes and why?
    Topoisomerases, to relieve strain in DNA
  10. Topoisomerase
    • Have catalytic TYROSINE, catalyzes phosphoryl-transfers
    • Activites:
    • DNA packaging
    • Genome replication
    • Chromosome segregation
    • Transcription/Expression
    • Recombination and Repair
    • Type I cut one strand, Type II cut both (gyrase)
  11. How a coil is added
    • Reaction is a phosphoryl transfer from base-base to base-tyrosine
  12. DNA packaging in eukaryotes
    • have DNA associated proteins called histones
    •  -H1, H2A, H2B, H3, H4 types
    • DNA wraps around histone
    •     -Nucleoprotein complex called nucleosome
    • Bacteria lack nucleosomes
  13. Nucleosomes are packaged into:
    30 bn Fibers
  14. 30 nm Fibers packaged into:
    Chromosomes

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