DNA QUESTION 1987:				L. PETERSON/AP BIOLOGY

	Describe the production and processing of a protein that will be exported 
	from a eukaryotic cell. Begin with the separation of the messenger RNA
	from the DNA template and end with the release of the protein at the plasma
	membrane.

  
  STANDARDS: 
  
  PRODUCTION:       Max. = 8 points
  (Points found in many papers)              (Points less frequently mentioned)
  RNA types:
  __  a) m-RNA single stranded               __ DNA termination signal exists
  __  b) t-RNA clover leaf                        and functions to dislodge the
  __  c) r-RNA + protein = ribosome                    growing RNA message.
  __  Ribosome consists of large and small subunits
  __  m-RNA moves through pores in the nuclear envelope
  __  m-RNA enters cytoplasm
  __  m-RNA associates with ribosomes or rough ER  __introns removed; exons spliced
                                        (pre m-RNA).
  __ initiating codon (AUG) exists on m-RNA        __5' end of m-RNA is capped  
  __  m-RNA read in 3 nucleotide groups/codons    (methylated guanine &/or
  __  amino acids joined to specific t-RNAs        poly-A tail added to the 3' end).
  __  anticodon binds to codon on m-RNA
  __  codon sequence determines amino acid sequence       __t-RNA has anticodon loop.
  __  PA sites exist in the ribosomes (2 codons fit in)
  __  peptide bonds form between the amino acids     __ribosomes and m-RNA move 
  __  translation of m-RNA ends at stop codon          with respect to each other.
         (UAA, UAG, UGA)                   __separation protein frees
                                        C terminal COOH from the
                                        t-RNA.
                                      __synthesis of the protein in
                                        N -> COOH direction.
                                      __m-RNA is read in the
                                        5' -> 3' direction.
  PROCESSING AND EXPORT:      NO MAX.
  
  __  ribosomes attach to outside of (rough) ER
  __  peptide enters ER (lumen)
  __  may be processing signal for entry into ER
  __ peptide moves to smooth ER
  __  transport vesicles form around polypeptide
  __  vesicles go to membrane or Golgi
  __  changes may occur in the protein in the Golgi Complex
        (- H2O, + sugar, + other peptides)
  __  proteins (vesicles) move to older parts (edge of Golgi)
  __  sorting of molecules into different types of Golgi sacs (lysosome) occur
  __  secretion vesicles bud off Golgi [movement]
  __  vesicles fuse with plasma membrane
  __  membranes break followed by release of contents