Transcript Chapter 11 Introduction To Genetics

Sect. 11-1
The Work of Gregor Mendel

Inheritance
 Characteristics
Passed From
Parents To Offspring

Genetics
 The
Study of Heredity and Its
Impact on Biology
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Born 1822
Austria
Studied University of
Vienna
Spent 14 yrs. Teaching
High School, Monastery
& Studying Pea’s
Studied Trait Transfer Between Stocks Of
Garden Peas

Mendel Succeeded Because His Pea Plants
Were:

True-Breeding Populations Were Available
 Produce Offspring Identical To Themselves

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Easily Visualized Characteristics
Reproduce Sexually
Pollination Could Be Controlled
They Have A Short Life Cycle
They Produce A Large Number of Offspring

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


Trait
Specific Characteristic That Varies
From One Individual To The Next:
 Seed Color, Shape, Coat Color, Pod
Shape, Color, Flower Position, Height
Page 264

P
Parents
F
Filial
(Offspring)
F1
First
Generation
F2
Second
Generation
Hybrid =
Offspring of Crosses Between Parents
With Different Traits.
Alleles =
Different Forms Of A Specific Gene
(different forms of a Trait)


Mendel Expected Blended
Offspring.
(Tall + Short = Medium)
That Did NOT Happen.
All Offspring Displayed A
Single Characteristic From One
Of The Parents.
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.
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!
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
Mendel Performed An F1 Cross
 You cross pollinate two plants from the F1
Generation
The missing allele re-appears in the
F2 Generation
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.
MOM
Egg 1
Egg 2
F1 Generation
Sperm 1
Sperm 2
DAD