biochem 012 DNA and protein synthesis part 5 (watson crick griffith chargoff's rule translation

  1. during termination, the A site accepts a protein called a _____ _____
    release factor
  2. how does the release factor terminate translation?
    the release factor causes the addition of a water molecule instead of an amino acid. This reaction releases the polypeptide and the translation assembly then comes apart
  3. what is a polyribosome (or polysome)?
    a number of ribosomes can translate a signle mRNA simultaneously, forming a polyribosome.
  4. is the protein functional after translation?
    usually, translation is not sufficient to make a functional protein and the polypeptide chains are modified after translation
  5. what types of proteins are made by bound ribosomes?
    bound ribosomes make proteins of the endomembrane system and proteins that are secreted from the cell
  6. true or false? polypeptide synthesis always begins in the cytosol?
    true. It begins in the cytosol. Synthesis finishes in the cytosol unless the polypeptide signals the ribosome to attach to the ER.
  7. polypeptides destined for the ER or for secretion are marked by a ____ ______
    signal peptide
  8. what is a signal-recognition particle?
    a SRP binds to the signal peptide and bring the signal peptide and its ribosome to the ER.
  9. what is a point mutation?
    chemical changes in just one base pair of a gene
  10. what are the two types of point mutations?
    • 1. base pair substitutions
    • 2. Base pair insertions or deletions
  11. what is a base-pair substitution?
    it replaces one nucleotide and its partner with another pair of nucleotides
  12. what is a silent mutation?
    they have no effect on the amino acid produced by a codon because of redundancy in the genetic code
  13. what is a missense mutation?
    a change in a codon resulting in a change in amino acid
  14. what is a nonsense mutation?
    a change in an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein
  15. what are insertions and deletions?
    these are additions or losses of nucleotide pairs in a gene. These mutations have a disastrous effect on the resulting protein more often than substitutions do
  16. insertion or deletion of nucleotides may alter the reading frame, producing a _______ ________
    frameshift mutation
  17. what are mutagens?
    they are physical or chemical agents that can cause mutations.
  18. viral genomes may consist of either:
    double or single-stranded DNA, or double- or single-stranded RNA
  19. what is a capsid?
    the protein shell that encloses the viral genome
  20. what is a capsomere?
    capsids are built from protein subunits called capsomeres
  21. true or false? all viruses have viral envelopes
    false, only some do
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biochem 012 DNA and protein synthesis part 5 (watson crick griffith chargoff's rule translation
biochem 012 DNA and protein synthesis part 5 (watson, crick, griffith, chargoff's rule, translation, ribosomes, mRNA) #27