The Work of Gregor Mendel Chapter 11 Section

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 7 Traits of Pea Plants

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 F 1 Generation F 1 (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 F 1 generation HYBRIDS

A Second Generation § Mendel let the F 1 generation self-pollinate and created a F 2 generation The white-flowering trait reappeared in the 2 nd Generation!! (3 Purple to 1 White)

Mendel’s Principles (in modern terms) 1. 2. 3. 4. 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? ? ?

MEIOSIS!!