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Chapter 16 (16.1 (Viruses (Alfred Hershey & Martha Chase; discovered…

- - - - Transformation; change in genotype and phenotype due to assimilation of external DNA by cells.
  - - - composed of DNA & protein
        
        DNA played an ongoing role inside the cell during infection process
      - T2 reprogram cells to produce viruses
  - - - confirm DNA was helical shape and showed spacing of nitrogenous base
      - Double strands; 2 strands present
      - Franklin; sugar-phosphate back bones
        
        Negative charged phosphate groups facing aqueous surrounding
        
        2 sugar phosphate backbones are antiparallel (subunits run in opposite directions
        
        8.4nm 1 full turn with base stacked .34nm apart. 10 layers base pairs
- - - - DNA polymerases proof read new DNA, replacing incorrect nucleotides
        
        In mismatch repair, enzyme correct errors that persist
        
        Nucleotide excision repair is a process by which nucleases cut out and other enzymes replaced damaged stretched of DNA
    - - Telomerse catalyze the lengthening of telomeres in germ cells
- - - - Histones bind to each other form nucleosomes
      - Histones tails extend outward from each bead-like nucleosome core
        
        Addition coiling and folding lead to high density of chromatin
- - - - or RNA molecules
  - - - or as a stop signal (3 codons)
- - - - untranslated region (5'UTR or 3'UTR) end of coding segment
  - - - Carried out by splicesomes but sometimes RNA can catalyzed its own splicing
        
        ability called ribozymes (derives from inherent properties of RNA
      - Prescence of introns allow for alternative RNA splicing
- - - - Promotor including TATA box in eukaryotic sets where RNA synthesis initiates
      - Transcription factors help eukaryotic RNA polymerase recognize promoter sequences forming transcription initiation complex
      - Termination differs in bacteria and eukaryotes
- - - - tRNA lines up its anticoden at complementary condon on mRNA
    - - Protein faciliates coupling with binding sites for mRNA and tRNA
      - coordinate 3 stages of translation; initiation, enlongation, and termination
        
        Formation of peptide bonds between amino acids is catalyed by rRNA and tRNA move through A & P sites and exit through E site
        
        After translation during protein process proteins may modified by cleavage or attached sugars, lipids, phosphate or other chem groups
        
        Free ribosomes in cytosol initiate synthesis of all proteins
        
        But genes with single peptide are synthesis by ER
        
        Gene can be transcribed by severa; RNA polymerases also single mRNA can translate form polyribosomes
        
        In bacteria the processes are coupled but in eukaryotic are separate and time by nuclear membrane