Warm-up

Warm-up1. 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.

2. 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)

Ch. 11-3 Exploring Mendelian GeneticsObjectives:

1. Explain the principle of independent assortment.

2. Describe the inheritance patters that exist aside from simple dominance.

3. Explain how Mendel’s principles apply to all organisms.

Independent Assortment1. The law of independent assortment – the

inheritance of one trait does not influence the inheritance of another trait.

A. For example, the alleles for seed color have no effect on the alleles for seed shape.

B. Mendel discovered this with a Two-Factor Cross

RRYY x rryy

(Round Yellow) x (Green wrinkled)

R = Round

r = wrinkled

Y = Yellow

y = green

Independent Assortment (cont.)1. F1 plants (RrYy) were crossed with each other to

determine if the alleles would segregate from each other in the F2 generation.

A. RrYy × RrYy

B. Independent assortment would mean the new combinations of phenotypes would be seen.

C. If independent assortment were not true only the original phenotypes would be observed.

Independent Assortment (cont.)

Mendel’s results: 9 : 3 : 3 :1 ratio in the F2 generation.

Patterns of Heredity can be Complex1. Polygenic trait – a characteristic controlled by

more than one gene.A. Many different phenotypic combos are seen in

offspring. The effect of one gene is difficult to trace.

B. Ex. Height, weight, skin, and hair color.

Patterns of Heredity can be Complex1. Incomplete Dominance – phenotype is

intermediate between two parents.A. Ex. Flower color in “Four O’Clock

plants”: Red and white flowered parents produce pink offspring.

Patterns of Heredity can be Complex1. Codominance – Two alleles are expressed at the

same time and both traits are seen.A. Ex. Roan horses: Have both red and white hairs.

1 parent = red, other parent = white.

1. Multiple alleles – some genes have three or more alleles for one trait.

Full color: CC, Ccch, Cch, or CcChinchilla: cchch, cchcch, or cchcHimalayan: chc, or chchAIbino: cc

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

Patterns of Heredity can be Complex

Patterns of Heredity can be Complex1. Traits influenced by environment:

A. 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

Patterns of Heredity can be Complex

Homework1. Read the section on p. 272 titled “A Summary of

Mendel’s Principles” and summarize Mendel’s four principles in your notebook.

2. Complete Cornell Notes

3. Ch. 11-3 RSW

4. Study your Flashcards!!

Mendel’s Principles and Complex Patterns of Heridity

1. Read pp. 272-274A. summarize Mendel’s four principles in your notebook

B. Explain with an example the following: Incomplete Dominance, Codominance, Multiple Alleles, and Polygenic traits.

2. Complete your Cornell Notes.

3. Complete your Ch. 11-3 RSW.

4. Study your Flashcards!