Warm-up

1. Warm-up • A green-leafed plant (LL) is crossed with a plant with yellow leaves(ll).  The cross produces the F1 generation: 185 green-leafed plants. (a) What is the genotype ratio of the 185 green leafed plants?(b)Give the genotype & phenotype ratio of the offspring that would be produced by crossing two of the F1 green-leafed plants obtained from the initial cross. • Mendel found that crossing wrinkle-seeded plants (ww) with pure round-seeded plants (WW) produced only round-seeded plants.What genotypes & phenotypes can be expected from a cross of a wrinkle-seeded plant & a plant heterozygous for this trait ? (include ratios for each)

2. Ch. 11-3 Exploring Mendelian Genetics • Objectives: • Explain the principle of independent assortment. • Describe the inheritance patters that exist aside from simple dominance. • Explain how Mendel’s principles apply to all organisms.

3. Independent Assortment • The law of independent assortment – the inheritance of one trait does not influence the inheritance of another trait. • For example, the alleles for seed color have no effect on the alleles for seed shape. • Mendel discovered this with a Two-Factor Cross RRYY x rryy (Round Yellow) x (Green wrinkled) R = Round r = wrinkled Y = Yellow y = green

4. Independent Assortment (cont.) • F1 plants (RrYy) were crossed with each other to determine if the alleles would segregate from each other in the F2 generation. • RrYy ×RrYy • Independent assortment would mean the new combinations of phenotypes would be seen. • If independent assortment were not true only the original phenotypes would be observed.

5. Independent Assortment (cont.) Mendel’s results: 9 : 3 : 3 :1 ratio in the F2 generation.

6. Patterns of Heredity can be Complex • Polygenic trait – a characteristic controlled by more than one gene. • Many different phenotypic combos are seen in offspring. The effect of one gene is difficult to trace. • Ex. Height, weight, skin, and hair color.

7. Patterns of Heredity can be Complex • Incomplete Dominance – phenotype is intermediate between two parents. • Ex. Flower color in “Four O’Clock plants”: Red and white flowered parents produce pink offspring.

8. Patterns of Heredity can be Complex • Codominance – Two alleles are expressed at the same time and both traits are seen. • Ex. Roan horses: Have both red and white hairs. 1 parent = red, other parent = white.

9. Patterns of Heredity can be Complex • Multiple alleles – some genes have three or more alleles for one trait. KEY C = full color; dominant to all other alleles cch= chinchilla; partial defect in pigmentation; dominant to ch and c alleles ch = Himalayan; color in certain parts of the body; dominant to c allele c = albino; no color; recessive to all other alleles Full color: CC, Ccch, Cch, or Cc Chinchilla: cchch, cchcch, or cchc Himalayan: chc, or chch AIbino: cc

10. Patterns of Heredity can be Complex • Traits influenced by environment: • An individual’s phenotype often depends on conditions in the environment. Ex. 1 hydrangea flower color of blue to pink depends on the acidity of the soil. Ex. 2 The artic fox’s coat color depends on the temperature: warm temps produce enzymes that cause a darker coat color. Therefore white in winter to blend in with the snow! Ex. 3 Human height is influenced by nutrition

11. Patterns of Heredity can be Complex

12. Homework • Read the section on p. 272 titled “A Summary of Mendel’s Principles” and summarize Mendel’s four principles in your notebook. • Complete Cornell Notes • Ch. 11-3 RSW • Study your Flashcards!!

13. Mendel’s Principles and Complex Patterns of Heridity • Read pp. 272-274 • summarize Mendel’s four principles in your notebook • Explain with an example the following: Incomplete Dominance, Codominance, Multiple Alleles, and Polygenic traits. • Complete your Cornell Notes. • Complete your Ch. 11-3 RSW. • Study your Flashcards!