DNA QUESTION 1974:					L. PETERSON/AP BIOLOGY

	Describe protein synthesis in terms of molecular structures of the 
	nucleic acids and, using a specific example, explain how a new 
	phenotypic characteristic may result from a change in DNA.

  
  STANDARDS:    1/2 point each for each of the following 
          (upper limit of points per section)
  DNA:
  __  double stranded
  __  helical form
  __  nucleotide
  __  phosphate-deoxyribose-purine or pyrimidine
  __  base pairing, A-T, G-C
  __  hydrogen bonds form the cross linkage
  __  separation of strands, "unzipping"
  __  strands antiparallel, sense and nonsense
  __  2 hydrogen bonds (A-T), 3 hydrogen bonds (G-C)        (max. = 4 points)
  mRNA:
  __  synthesized on DNA sense strand template, bases complementary
  __  nucleotides
  __  phosphate-ribose-purine or pyrimidine (U, A, G, C)
  __  RNA polymerase bonds nucleotides together
  __  mRNA synthesized in nucleus, moves to cytoplasm
  __  codon(s), triplets of bases, specific for an amino acid
  __  start, stop, and nonsense codons (43 possible combinations)
  __  attachment to ribosomes
  __  ribosomes move along it, reading message codon by codon
  __  instructions for synthesis of polypeptides
  __  amino acid sequence is ordered along it
  __  specific examples of "start" and "stop"
  __  mention of rRNA                             (max. = 5 points)
  tRNA:
  __  temporary attachment to mRNA, base-pairing
  __  anticodon complements codon of mRNA
  __  each tRNA is specific for one amino acid
  __  carries it to ribosome
  __  peptidyl transferase - joins amino acids by peptide bonds
  __  specific enzymes, glutathione, Mg ++ required for attachment of amino acids
  __  amino acid must first be activated by ATP
  __  ATP energy goes to peptide bond formation             
  EXAMPLES (only one may be used):           (max. = 3 points)
  one point for legitimate examples: 
  (sickle cell anemia, E. coli, tryptophan synthetase, Neurospora work, alkaptonuria, albinism)
  __  hypothetical case
  
  __  change in DNA, resulting
  __  change in mRNA code
  __  change in tRNA
  __  change in protein
  __  change in phenotype                         (max. = 3 points)