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Chapter 11 Introduction To Genetics

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					Introduction To Genetics


 The Work of Gregor Mendel



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          Gregor Mendel
• Born 1822
• Austria
• Studied University of
  Vienna
• Spent 14 yrs.
  Teaching High School,
  Monastery & Studying
  Pea’s

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         Gregor Mendel
• Inheritance
 –Characteristics Passed From
  Parents To Offspring
• Genetics
 –The Study of Heredity and Its
  Impact on Biology

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     Gregor Mendel’s Peas
Studied Trait Transfer Between Stocks Of
                Garden Peas




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Gregor Mendel’s Peas




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      Gregor Mendel’s Peas
• Mendel Succeeded Because His Pea Plants
  Were:
  – True-Breeding Populations Were Available
     • Produce Offspring Identical To Themselves
  – Easily Visualized Characteristics
  – Reproduce Sexually
  – Pollination Could Be Controlled
  – They Have A Short Life Cycle
  – They Produce A Large Number of
    Offspring
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     Gregor Mendel’s Peas
• Cross Pollinating Peas
  – Instead of Self Pollination, The Pollen
    From One Plant Is Used To Pollinate
    The Egg Cells of Another Plant.
  – Cut Away Anthers
  – Hand Pollinated Using Pollen From A
    Chosen Plant


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Pollination Process




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Pollination Process




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        Genes & Dominance
Trait
  – Specific Characteristic That Varies
    From One Individual To The Next:
  – Seed Color, Shape, Coat Color, Pod
    Shape, Color, Flower Position, Height




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Genes & Dominance

 P           Parents

               Filial
 F          (Offspring)
             First
 F1        Generation
            Second
 F2        Generation
     Genes & Dominance

Hybrid =
     Offspring of Crosses Between
     Parents With Different Traits.

Alleles =
   Different Forms Of A Specific
   Gene (different forms of a Trait)
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       Genes & Dominance
 Mendel Expected Blended
           Offspring.
  (Tall + Short = Medium)
   That Did NOT Happen.
• All Offspring Displayed A
  Single Characteristic From
  One Of The Parents.

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            Mendel’s Proof
F1 Generation (1st Generation)
  – One of the Alleles
                                                    P
    Disappeared (short)
  – Where did it go?
  – Was it destroyed?
                                                    F1
   F1 Generation – All Plants Were TALL



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            Mendel's Proof
Mendel Performed An F1 Cross
• You cross pollinate two plants from the F1
  Generation




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        Mendel's Proof
The missing allele re-appears in the
           F2 Generation




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   Mendel’s Proof




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    Genes & Dominance
    Mendel’s Hypothesis
1. Biological Inheritance
 • Is Determined By Factors That Are
   Passed To The Next Generation
2. Principle Of Dominance
 • Some Alleles Are Dominant And
   Some Are Recessive.

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           Mendel’s Proof
Key Concept:
  When Each F1 Plant Flowers,
  – The Two Alleles Are Segregated From
    Each Other So That The Gamete Carries
    Only A Single Copy Of Each Gene.
  – Therefore, each F1 plant produces two
    types of gametes – one Tall and one Short.



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              Segregation
            Segregation:
  Separation of Alleles During Gamete
                Formation

Remember: There are two copies (alleles)
   of each gene in each cell. One came
      from Mom, the other from Dad!
        The same is true in peas!

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          Mendel’s Proof
        MOM         F1 Generation         DAD




Egg 1                         Sperm 1



Egg 2                         Sperm 2




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