The Monk who loved peas

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The Monk who loved peas

• How to Make a Living Thing

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Gregor Mendel

• Monk, failed teacher, pea-lover, genetic genius
• From growing peas, Mendel noticed that offspring
  did not always have the same traits as the
  parents
• But then the parents trait would show up again
  in a grandchild, or 2nd generation
• So Mendel began to experiment, attempting to grow
  peas with certain traits, or characteristics

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The Proof is in the Peas

• Peas were an excellent choice for his research
  for two reasons
• They can self-pollinate, creating offspring with
  the same traits as the parent
• Or, they can cross-pollinate with other peas

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The Experiment

• Mendel looked at one characteristic at a time
  (color, height, shape)
• If a pea plant has a white flower, then it
  self-pollinates, youll have offspring with white
  flowers
• What happens if a purple-flowered pea plant
  cross-pollinates a white-flowered pea plant?

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Mendels Discovery

• Mendel noticed the offspring of a purple-flowered
  pea plant and a white one was always purple
• BUT, the grandchildren or 2nd generation, would
  have 1 white-flowered pea plant for every three
  purple ones

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Dominant Traits

• Dominant traits are the ones always showing up in
  the first generation
• The purple-flowered pea plant
• In a Punnett Square, dominant traits are
  symbolized by a capital letter

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Recessive Traits

• Fade into the back
• The white-flowered pea plant
• These traits reappear in the 2nd generation
• MUST be paired with another recessive allele

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Incomplete Dominance

• Sometimes, one trait is NOT dominant over the
  other
• Each allele provides some influence
• Hair texturecurly, straight, and wavyis an
  example in humans

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Genes

• The instructions for one particular trait are
  called a gene
• You have 2 forms of the same gene for every
  characteristic
• 1 from Mom, 1 from Dad
• Hair color, eye color, height, hitchhikers
  thumb, etc.

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Alleles

• The form of a trait given by one parent
• So, for each gene, you have 2 alleles
• Either dominant (capital letter) or recessive
  (lower-case)

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Genotype and Phenotype

• Both inherited traits form a genotype
• --Aa rr etc.
• The appearance of a characteristic is the
  organisms phenotype
• --a purple flower wrinkled peas wavy hair

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Genetic Probability and Pedigrees

• Probability is the mathematical chance of an
  outcome
• Aa x Aa has a 25 chance of getting aa as an
  outcome 25 AA 50 Aa
• Pedigrees are like family trees for determining
  the probability of genetic diseases like cystic
  fibrosis