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The Work of Gregor Mendel. Chapter 11, Section 1. Chapter 11: Introduction to Genetics. Genetics is the scientific study of heredity, or the passing of characteristics from one organism to another. Gregor Mendel (1822-1884).
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The Work of Gregor Mendel Chapter 11, Section 1
Chapter 11: Introduction to Genetics Genetics is the scientific study of heredity, or the passing of characteristics from one organism to another
Gregor Mendel (1822-1884) • An Austrian monk who used a scientific approach to study inheritance • He is considered the “Father of Genetics” • There was no knowledge of genes or DNA at the time • He studied inheritance patterns in pea plants…Why? • Contrasting traits or characteristics • Reproduce sexually, quickly, and have many offspring • Accessible and easy to handle
Controlled Reproduction Stamen(♂) produces pollen Carpel/Pistel(♀) produces ovules (eggs) Removing immature stamen prevents self-fertilization
Sexual Reproduction in Plants Fertilization: Occurs when male and female sex cells join Cross-pollination: Pollen from one plant fertilizes(pollinates) egg of another plant Self-pollination: Pollen and eggs come from the same flower
Mendel’s Experiments • Mendel identified stocks of plants that were TRUE-BREEDING for a particular trait Tall Plant self-pollination All Tall Offspring • Mendel crossed two true-breeding plants with contrasting characteristics (ex: purple flowers and white flowers) • He called them the P generation (for Parental) What do you think the offspring looked like?
Mendel’s F1 Generation F1 (for Filial) or “son” in Latin! The offspring were 100% Purple Flowering Mendel repeated this experiment and observed similar results with all 7 of the traits he studied! He called the F1 generation HYBRIDS
A Second Generation • Mendel let the F1 generation self-pollinate and created a F2 generation The white-flowering trait reappeared in the 2nd Generation!! (3 Purple to 1 White)
Mendel’s Principles (in modern terms) • Traits are passed from one organism to another by units called genes. There are different forms of genes called alleles. Ex: Gene: height Alleles: tall, dwarf • Genes are inherited in pairs, one allele from each parent Homozygous: identical alleles Heterozygous: different alleles • In a hybrid, only the dominant allele (T) will be expressed (or seen). The other allele is recessive (t). • Alleles segregate (separate) from each other during gamete formation and rejoin during fertilization to make the offspring
Principle of Segregation What process segregates the alleles during gamete formation???