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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 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 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