AP Biology · Summary

Unit 6 summary

  1. DNA strands are antiparallel and complementary: A with T, G with C. RNA is single-stranded with ribose and U.
  2. DNA polymerase adds only to a 3' end, so new strands grow 5' to 3': the leading strand in one piece, the lagging strand in Okazaki fragments joined by ligase.
  3. mRNA matches the coding strand with U for T; eukaryotes add a cap and tail and splice out introns.
  4. Read codons from AUG to a stop codon; a stop codon adds no amino acid.
  5. Inducible operons turn on when an inducer removes the repressor; repressible operons turn off when the end product activates it.
  6. Cells with the same DNA differ because different transcription factors and chromatin states turn on different genes.
  7. A substitution changes one codon, so it is silent, missense or nonsense; an insertion or deletion not a multiple of three shifts the frame. On a gel, short fragments run farthest.