DNA

DNA

Central Dogma
1. DNA
  1. Genetic Material
  2. Contains all hereditary info
  3. nucleic
2. RNA-Transfer Material
  1. Transcribed from DNA
  2. Transports info outside of nucleus
  3. Transient Life
3. Protein
  1. Structural/Catalytic
  2. Translated from RNA
POLYMER OF NUCLEOTIDE MONOMERS
1. PURINE/PYRIMIDINE
  1. Purine
    1. adenine
    2. guanosine
  2. Pyrimidine
    1. cytosine
    2. thymine
  3. @ 1' OH of Pentose
2. 2' OH- RNA, 1' H-DNA
3. PO42- attached @ C5, PO42- of next nucleotide @C3'-glycosidic bond
Packaging
1. Prokaryotic
  1. ~1m supercoiled and compacted, attached to scaffold extranuclearly
2. Eukaryotic
  1. DNA is supercoiled into chromatin
    1. Chromatin-DNA interacting with nucleus
    2. Chromatin is folded into "beads on a string" via nucleosomes~30nm fiber
    3. 30nm-> superloop->rosette (6 loops)->coil (30 rosettes)->2 chromatids (10 coils)
Replication
1. HELICASE unwinds parental dsDNA
  1. ssDNA binding proteins stabilize unwound strand
    1. leading strand synthesized continually in 5' -> 3' direction
      1. lagging strand synthesis is discontinuous, short primer synthesis by PRIMASE
        RNA primer replaced by DNA, Okazaki fragments joined by DNA ligase to growing strand
2. DNA polymerase
  1. by
  2. Extends short primer to form Okazaki
  3. replaces primer
Transcription
1. RNA Polymerases
  1. Prokaryotic
    1. single core protein w/ 5 subunits
      1. β'-largest part of active center
      2. β-Remainder of active center
      3. α1 & α11-Dimer interacting w/ & transcription factors
      4. ω-facilitates assembly & protein stability
      5. σ factor- provides promoter binding specificity
  2. Eukaryotic
    1. I- synthesizes pre-rRNA (45S, 35S in yeast)
      1. matures into 28S, 18S & 5.8S rRNAs
      2. form major RNA sections of ribosome
    2. II- precursors of mRNA and snRNA & microRNA
      1. requires many transcription factors for promoter binding
    3. III-synthesis of tRNA, rRNA 5S & small RNAs w/in nucleus & cytosol
2. Mediator complex
  1. receive all signals from activator proteins
  2. Compile message
  3. transmit message to RNA P II
  4. Also bind to DNA sequences known as enhancers as far as 1000s of bps from promoter
3. Start site has +1, anything to right is (+), left is (-)
Translation
1. Initiation
  1. Ribosome binds mRNA @ start codon
  2. Prokaryotic
    1. 30S-> reacts with 50 S -> forms 70S
  3. Eukaryotic
    1. e1F4E released, e1F4F complex binds to mRNA cap--> 2° structure unwinds & 48 S forms-->scanning, initiation factors released & 80S formed
2. Elongation
  1. Succesive addition of amino acids elongates polypeptide chain
3. Termination
  1. Polypeptide is released & ribosome dissociates once stop codon is reached
Gene Structure
1. Prokaryotic
  1. Transcription & Translation linked
    1. As mRNA is made, serves as a template for protein formation
2. Eukaryotic
  1. Promoter binds upstream from potential regulatory elements
    1. Introns removed during splicing-basis of fetal development
      1. Initial translation product- amino acid chain
        Posttranslational modifciation--> finished protein

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