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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