AP Biology Unit 5: Heredity — Mind Map

Reviews Mendelian genetics (monohybrid and dihybrid crosses, test crosses), pedigrees, sex-linked vs. autosomal inheritance, linkage and crossing over, chromosomal disorders, non-Mendelian patterns (codominance, incomplete dominance, pleiotropy), and meiosis as a source of genetic variation.

• Heredity
  • Mechanisms of Variation
    • Crossing Over
      • Occurs in Prophase I
      • Exchange between non-sister chromatids
      • Creates recombinant chromosomes
    • Independent Assortment
      • Random orientation in Metaphase I
      • Formula: 2^n combinations
      • 8.4 million possibilities in humans
    • Random Fertilization
      • Random union of unique gametes
      • Multiplies meiotic variation
  • Genetic Linkage and Mapping
    • Linked Genes
      • Located close on same chromosome
      • Inherited together as a unit
      • Recombination frequency < 50%
    • Linkage Maps
      • Based on recombination frequencies
      • 1% RF = 1 centimorgan (map unit)
      • Distance reflects crossover probability
  • Non-Nuclear Inheritance
    • Maternal inheritance
    • Mitochondrial DNA
    • Chloroplast DNA in plants
  • Environmental Effects
    • Phenotypic Plasticity
      • One genotype, multiple phenotypes
      • Influence of temperature and pH
      • Nutrition and UV exposure
  • Meiotic Errors
    • Nondisjunction
      • Failure of chromosomes to separate
      • Results in aneuploidy
      • Examples: Down and Turner syndromes