Inheritance Darwin and Wallace Natural selection model Offspring resemble their parents closely Offspring inherit traits from their parents How? Mendel's Experiment Looked at flower color True breed red True breed white Lecture: Mendelian Inheritance Inheritance Gregor Mendel Diploid model Allele Phenotype Genotype Homozygous Heterozygous Mode of Inheritance Codominant Dominant/Recessive Gregor Mendel Interested in inheritance Worked with pea plants Pea Plants P1 True Breed Red x True Breed White F1 100% Pink offspring 1 Blending inheritance ? Pea Plants F1 Pink x Pink F2 Red Pink White 25% 50% 25% Pea Plants How did this happen? Mendel develops a hypothesis Pea Plants Took some of the pink offspring and crossed them Blending inheritance does not work Mendel's Model Units of inheritance are particulate All individuals have 2 units for each trait Each parent passes 1 unit for each trait to their offspring Equal probability for inheritance of each unit 2 Pea Plants P1 True Breed Red x True Breed White RR WW Pea Plants P1 True Breed Red x True Breed White RR WW F1 100% Pink RW Pea Plants F1 Pink x Pink RW RW F2 Red Pink White 25% 50% 25% RR RW WW Punnett Square Pea Plants F1 Pink x Pink RW RW Next, he tries seed pod color 3 Seed Pod Color True breed yellow True breed green Seed Pod Color Takes some of the offspring and crosses them F1 Yellow x Yellow F2 75% Yellow 25% Green