; Chapter 11 Introduction to Genetics
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Chapter 11 Introduction to Genetics


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									      Chapter 11
Introduction to Genetics
       Mrs. Craun
               Gregor Mendel
• Born in 1822, died in 1884
• Austrian Monk
• Studied Science and Math at the University of
• Tended a monastery Garden and taught high
• Considered the “Grandfather of Genetics”
   How did Mendel
   study genetics?

• By trade, Mendel was a mathematician and studied
• As part of his duties, he took care of the monastery
• He noticed that offspring tended to have the same
  characteristics as the parents
  – Remember…no one knew anything about DNA in the
    What traits did Mendel study in
              pea plants?
•   Seed shape
•   Seed color
•   Seed coat color
•   Pod shape
•   Pod color
•   Flower position
•   Plant height
How did Mendel study genetics?

   Mendel first looked at true-breeding
   plants, and then cross-pollinated them
              creating hybrids
            Terms to Define
• true-breeding:

• cross-pollination:

• hybrid:
Mendel’s Breeding Program
Mendel’s Breeding Program
             • P generation: parent
  Hybrid Cross
• Did Mendel see a
  combination of
  parental traits in
  hybrid offspring?

  – offspring = F1 generation
     • F1: filial generation
    Mendel’s Conclusions from the
          First Experiment
•   Inheritance must be determined by factors
    passed from one generation to the next
    –   We now know these as the genes found on your
•   Principle of Dominance
    –   Mendel realized some traits are dominant and
        others are recessive
    –   Dominant alleles “overpower” recessive alleles,
        so only the dominant characteristics are seen
        when they combine.
      Mendel’s First Cross:
only one parent’s traits were seen
        in F1 generation
   Mendel’s Second Experiment
• Mendel wondered if the recessive alleles
  were still present(perhaps just hidden?).
• He let his F1 generation plants self-pollinate
  – self-pollination:
   Mendel’s Second Experiment
• F1 generation self-
  pollinates 
         F2 generation
• Notice that the
  recessive trait (white
  flowers) shows up
  again although the
  parent was pink
    Mendel’s Conclusion from Second
• Remember: Organisms
  have two copies of each
  gene in their cells- one
  from the mom and one
  from the dad
• During meiosis these two
  copies are duplicated and
  then separated, so that
  each gamete has only one
  copy of the
Mendel’s Conclusion from Second
   Mendel’s Conclusion from Second
principle of segregation: two copies of a gene
   separate, or segregate during the formation
                 of egg and sperm
    …we now know this happens through the
                process of meiosis
          Mendel’s Principles
1- dominance and recessivness: two forms for
   every trait; one form masks (dominant) the other
2- segregation: genes separate during the formation
   of egg and sperm
3- independent assortment: no two genes are
   connected and separate independently of each
   other during formation of egg and sperm
       - no two traits are connected

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