Download Mendel

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
F
Filial
(Offspring)
F1
First
Generation
F2
Second
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
Disappeared (short)
– Where did it go?
– Was it destroyed?
P
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
Egg 1
Egg 2
F1 Generation
DAD
Sperm 1
Sperm 2
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