Gregor Mendel

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Gregor Mendel

• Chapter 10

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Gregor Mendel

• Gregor Mendel Father of Genetics
• Austrian monk
• Conducted several experiments on pea plants
• His work lead to the foundation of modern
  genetics

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Mendels Experiments

• Cross-Pollination breeding of 2 different plants
  (pea plants)
• P generation parent original strains
• purple x white
• F1 generation filial offspring of P gen.
• all appear purple
• F2 generation offspring of self-pollinating F1
  gen.
• 3/4 are purple, 1/4 white

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Why Peas???

• 1) Peas have distinct characteristics which could
  easily be studied
• Height, flower color, pea shape, etc.
• 2) Mendel could control pea reproduction
• He could cross-pollinate them OR make them
  self-pollinate
• 3) Mendel chose true-breeding plants
  (homozygous)
• Caused the recessive trait (white flowers) to be
  hidden in F1 gen., then reappear in F2 gen.

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Mendels Principles

• Principle of Dominance
• Some alleles are dominant others are recessive
• Law of Independent Assortment
• Each adult has 2 alleles/gene one from each
  parent
• Alleles for different genes separate
  independently

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Exceptions to Mendels Principles

• 1) Incomplete Dominance phenotype is in between
  those of parents
• i.e. hazel eyes, wavy hair
• 2) Codominance both alleles are expressed in
  phenotype
• i.e. 2 diff. color eyes, spots in animal fur

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Exceptions to Mendel (cont)

• 3) Multiple Alleles gene has more than 2 alleles
  
• Results in more possible combinations
• Individuals still only inherit 2 alleles
• i.e. blood type 3 alleles
• 4) Polygenic Traits traits controlled by 2 or
  more genes
• Leads to wide range of phenotypes
• i.e. skin color 4 genes

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