Please enable JavaScript.

Coggle requires JavaScript to display documents.

Chapter 16 & 17 (DNA structure (Chargaffs rules (Base varies (AGCT),…

- - - - Loosely packing chromatin
    - - Regions of chromatin that is highly condensed
      - Make it difficult to express genetic information
- - - - Initial nucleotide strand is a short RNA
      - Synthesized by enzyme primase
      - Short (5-20 nucleotides long)
      - 3' starter point
    - - Catalyze the synthesis of new DNA @ replication fork
      - Most require primer primer & DNA template strand
    - - Lagging strand is synthesized as series of segments
      - Joined together by DNA ligase
    - - Primase synthesizes a short RNA primer
      - DNA Pol 3 sharts DNA synthesis @ 3' end of primer, continues in 5' to 3' direction
      - DNA Pol 1 replaces RNA primer with DNA nucleotides
      - Lagging strand synthesized in okazaki fragment, later joined by DNA ligase
  - - - Repair enzymes
    - - Nuclease cuts/replaces damaged stretch of DNA
      - DNA polymerase & DNA ligase follow
  - - - Postpose erosion of genes near end of DNA molecules
      - Might be connected to aging
      - Evidence in cancer cells
- - - - Proteins/polypeptide
  - - - Noncoding regions
      - May regulate gene expression
      - Alternative RNA splicing
        
        Genes encoding more than one polypeptide
    - - Eventually expressed
      - Usually translated into amino acids
      - Domains
        
        Modular architecture consisting of discrete regions
        
        Different exons code for different domains in a protein
        
        Shuffling may result in new protein
    - - Variety of proteins& small RNAs recognize splice sites
      - Can also catalyze the splicing reaction
  - - - P: holds tRNA that carries growing polypeptide chain
      - A: holds tRNA that carries next amino acid added to the chain
      - E: exit site, discharged tRNAs leave the ribosome
    - - Can switch from free to bound vice versa
      - Free (cytosil)
        
        Synthesize proteins that function in cytosol
      - Bound (attached to ER)
        
        Make proteins for endomembrane system & proteins secreted from cell
        
        Signal peptide
        
        Polypeptide s destined for ER/ secretion
        
        Signal- recognition partical (SRP) binds to signal peptide
        
        Escorts the ribosome
  - - - Changes in just one nucleotide pair of a gene
      - Can lead to production of denatured protein
      - Single nucleotide
        
        Pair substitution
        
        Replaces one with it's partner
        
        Silent mutations
        
        No effect on amino acid produced by codon
        
        Missense mutations
        
        Not the correct amino acid
        
        Nonsense mutations
        
        Change amino acid into a stop codon
        
        Most lead to denatured proteins
      - Nucleotide pair
        
        Frameshift mutation
        
        May alter the reading frame
        
        Mutagens
        
        Physical/chemical agents that cause mutations
- - - - Match between tRNA &amino acid
      - Done by enzyme aminoacyl- tRNA synthetase
      - Wobble
        
        Flexible pairing @ the 3rd base of a codon
        
        Allows some tRNAs to bind to more than one codon
    - - Building polypeptide
      - Energy& protein "factors" required
      - Initiation
        
        AUG (start codon) signals the start
        
        Ribosomal subunit binds w/ mRNA & tRNA
        
        Moves along mRNA til it reacts AUG
        
        Initiation factors (proteins) brings large subunit that completes
      - Elongation
        
        Amino acids added one @ a time
        
        3 steps
        
        Codon recognition
        
        Peptide bond formation
        
        Translocation
        
        5'-3' direction
      - Translation
        
        Site accepts a protein called release factor (adds H20)
        
        Reaction releases the polypeptide, translation assembly comes apart
        
        Polypeptide chains modified after/ targeted @ specific sites in cell
      - Post translational modifications
        
        Begins to couldn't & fold
        
        Gene determines primary structure
  - - - Pries DNA strands apart & joins together RNA nucleotides
      - Doesn't need any primer
      - RNA synthesis catalyzed by
      - Attached to the promoter
      - Bacteria
        
        Terminator
        
        Signals end of transcription
    - - Stretch of DNA that is transcribed
    - - Mediate the binding of RNA polymerase
    - - Completed assembly of transcription factors &RNA polymerase 2
      - Bound to promoter
    - - Promotoer
      - Crutial in forming initiation complex of eukaryotes
    - - Both ends are altered
    - - Pre-mRNA
        
        5': nucleotide 5' cap
        
        3': poly-A tail
      - Several functions: protect mRNA from hydrolytic enzymes