Ch Mendel’s Discoveries Objectives: 1.Compare and contrast the blending hypothesis and the particulate hypothesis of inheritance. 2.Describe the methods Mendel used in his plant-breeding experiments. Vocab: Trait Genetics Cross-fertilization

Gregor Mendel Austrian monk “Father of Modern Genetics” (Study of heredity) Breed pea varieties.

Pre-Mendel Blending Hypothesis: Offspring have a blend of parent traits. Ex: Red x White flower --> Pink flowers --> Pink in next generation too. Problem: Red and white flowers appear again in future generations; traits are not really blended.

Background Vocab.  True-breeds: pure gene lines – offspring match parent  Self-pollination: pollen from flower fertilizes the same plant  Cross-fertilization: pollen will fertilize a different plant  Hybrid: Cross between organisms with different traits (blonde hair & brown hair)  Trait: Physical characteristics

Mendel’s Pea Traits

Cross-Pollinating

Mendel’s Crosses TRAIT 1: Seed Shape P Cross: Round v. Wrinkled F1 Phenotype: Round *P = parents *F1 = “filial” = “son”= off-spring

Mendel’s Crosses TRAIT 2: Seed Color P Cross: Green v. Yellow F1 Phenotype: Yellow

Mendel’s Crosses TRAIT 3: Flower Color P Cross: Purple v. White F1 Phenotype: Purple

Mendel’s Crosses TRAIT 4: Pod Shape P Cross: Inflated v. Pinched F1 Phenotype: Inflated

Mendel’s Crosses TRAIT 5: Pod Color P Cross: Green v. Yellow F1 Phenotype: Green

Mendel’s Crosses TRAIT 6: Flower Position P Cross: Axial v. Terminal F1 Phenotype: Axial

Mendel’s Crosses TRAIT 7: Plant Height P Cross: Tall v. Short F1 Phenotype: Tall

Mendel’s Conclusions Biological inheritance is determined by chemical factors passed from one generation to the next (Particulate hypothesis) –Geneticists now refer to these factors as genes –Genes can come in more than one form, each form is an allele ex. B or b (The “B” gene w/ 2 alleles)

Ch Mendel’s Genetics Objectives: 1.Explain Mendel’s principle of segregation. 2.Describe how probability applies to genetics. 3.Contrast genotype and phenotype. 4.Explain Mendel’s principle of independent assortment. Vocab: HybridRecessive Monohybrid crossPunnett square AllelePhenotype Homozygous Genotype Heterozygous dominantTestcross Dihybrid cross

More Genetics Vocab Homozygous: two identical alleles (AA or aa) Heterozygous: two different alleles (Aa) Phenotype: Physical appearance Genotype: Genetic make-up –Homozygous dominant (AA) –Homozygous recessive (aa) –Heterozygous (Aa)

Mendel’s Principles 1.There are alternative forms of genes (alleles) 2.There are 2 alleles for each trait (BB,Bb, bb) * we now know there can be more. 3.Some alleles are dominant; some recessive. Dominance: a recessive allele will be masked by a dominant allele 4.Principle of SEGREGATION: Alleles for each trait segregate (separate) during gamete formation (Anaphase I of meiosis)

Monohybrid Crosses = Parents differ in only 1 trait Results: F1: all purple F1 purples self- fertilize to see if white trait was lost. F2: 75% purple; 25% white White trait NOT lost!

Diagram that shows all possible outcomes of a genetic cross

Phenotype & Genotype Ratios Phenotype Ratio 3 Purple: 1 White Genotype Ratio 1 PP: 2 Pp: 1pp

-Reveals unknown genotype thru. Ratios - Unknown (Dominant phenotype) x homozygous recessive

Mendel’s DIHYBRID CROSSES Independent Assortment: Alleles for different traits do not influence each other’s segregation.

Dihybrid Cross F2: 9:3:3:1 Ratio Traits are inherited separately.