AP Biology · Summary

Unit 5 summary

  1. Meiosis I separates homologs and halves the chromosome number; meiosis II separates sister chromatids.
  2. Crossing over, independent assortment (2 to the power n combinations) and random fertilization make offspring vary.
  3. Work each gene on its own, then multiply: Aa x Aa gives 3/4 dominant, and independent genes give 9 : 3 : 3 : 1.
  4. Chi-square = the sum of (observed - expected) squared / expected; degrees of freedom = classes - 1; a value above the critical value means reject the hypothesis.
  5. Incomplete dominance gives an in-between heterozygote; codominance shows both traits; many genes give smooth, polygenic variation.
  6. Males have one X, so recessive X-linked traits show more often in males; sons get their X from their mother.
  7. Linked genes recombine only by crossing over; recombination frequency in percent is about the distance in map units, up to about 50.