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  • 1. Launch
    • In humans, tongue rolling is a dominant trait, those with the recessive condition cannot roll their tongues. Bob can roll his tongue, but his mother could not. He is married to Sally, who cannot roll her tongue. What is the probability that their first born child will not be able to roll his tongue?
    • A tall plant of unknown genotype is test-crossed. Of the offspring, 869 are dwarf and 912 are tall. What is the genotype of the unknown parent? Show the cross to prove it.
  • 2. Some terminology….
    • Modes of inheritance for a gene
      • X-linked- means its carried on the X axis
      • Y-linked- means its carried on the Y axis
      • Autosomal- refers to the fact its carried on any of the chromosomes labeled 1-22.
  • 3. Some terminology….
    • We write X-linked like this:
  • 4. Some terminology….
    • We write Y-linked like this:
  • 5. Some terminology….
    • We write autosomal like this:
  • 6. Practice
    • Set up the following crosses:
      • Cross 1: Two heterozygote's for a gene for knee size, found on the 7 th chromosome
      • Cross 2: A man with hemophilia crossed with a woman who has no traces of it in her family
      • Cross 3: A gene that affects semen development in males
  • 7. To calculate the number of phenotypes…
    • In a cross, to calculate the number of phenotype combinations individually for each gene and then multiply them.
  • 8. Practice
    • Calculate the number of phenotypes for this cross
      • Cross 1: TT x Tt
      • Cross 2: Tt x Tt
      • Cross 3: TTWW x ttww
      • Cross 4: TtWw x TtWw
      • Cross 5: TTWw x Ttww
      • Cross 6: AABbCc x AaBBcc
  • 9. Homework Packets