1. Monday, January 10, 2011  Objective: SWBAT complete Dihybrid Punnett squares.  Bellringer: Use a Punnett square to predict the offspring of parents that are hybrid dominant and homozygous recessive for the trait of Furriness (use the letter F).

2. Agenda 1. Bellringer 2. Guided notes: Dihybrid Crosses 3. Practice problems 4. Homework: SpongeBob Dihybrid Crosses

3. DIHYBRID PUNNETT SQUARES Mastering the Dreaded Dihybrid

4. What’s the difference?  When only ONE trait is looked at  For example, height OR color  Use a 2x2 Punnett square  When TWO traits are looked at  For example, height AND color  Use a 4x4 Punnett square Monohybrid crossDihybrid cross

5. Steps to complete a Dihybrid Cross 1. Determine the genotypes of the parents. 2. Figure out the possible gamete combinations for each parent. (gametes = sex cells)  Each gamete gets one copy of each gene.  Helpful Hint: Use the FOIL method to make pairs. 3. Complete the 4x4 Punnett square.  Helpful Hint: Complete one gene (one letter type) and then the second gene (the second letter). Note: These are the same as for a Monohybrid Cross, but now you’re doing them for two genes rather than just one!

6. Step by Step Dihybrid Example

7. What are the possible genotypes and phenotypes of the children of parents that are heterozygous for round eyes with a blue body and purebred for round eyes and hybrid for a yellow body? An Example Problem

8. Step 1: Determine the genotypes of the parents.  heterozygous for round eyes  blue body  purebred for round eyes  hybrid for a yellow body Parent 1:Parent 2:

9. Step 2: Figure out the possible gamete combinations for each parent. (gametes = sex cells) Parent 1:Parent 2: Each gamete gets one copy of each gene. Helpful Hint: Use the FOIL method to make pairs. FOIL pairs = First, Outer, Inner, Last RyRyRyRyryryryry Gametes: FirstOuterInnerLast RYRYRyRyRYRYRyRy Gametes: First Outer Inner Last

10. Step 3: Complete the 4x4 Punnett square. Parent 1:Parent 2: Helpful Hint: Complete one gene (one letter type) and then the second gene (the second letter). RyRyRyRyryryryry Gametes: RYRYRyRyRYRYRyRy RyRyRyRyryryryry RYRY RyRy RYRY RyRy R R R R R R R R r r r r r r r r R R R R R R R R R R R R R R R R y y y y y y y y y y y y y y y y Y y Y y Y y Y y Y y Y y Y y Y y

11. Genotype & Phenotype Ratios  Genotypes:  4 RRYy : 4 RrYy : 4 RRyy : 4 Rryy  Phenotypes:  8 Round-eyed, yellow body : 8 Round-eyed, blue body RyRyRyRyryryryry RYRY RyRy RYRY RyRy R R R R R R R R r r r r r r r r R R R R R R R R R R R R R R R R y y y y y y y y y y y y y y y y Y y Y y Y y Y y Y y Y y Y y Y y

12. Homework  Complete the practice problems from the notes.  Complete the Bikini Bottom Dihybrid Practice problem set.  If you didn’t yet take last Friday’s QUIZ, please come see me in room 109 after school or during your lunch period to take the Quiz. (We will go over the Quiz tomorrow.)