1. Dihybrid Crosses: Setting Up Punnett Square A cross involving two pairs of contrasting traits Round & Tall x wrinkled & Short (RrTt x rrtt) Use ‘FOIL’ method to find all combinations of alleles in the gametes (First, Outer, Inner & Last) Ex. Heterozygous round & tall = RrTt Gametes: RT, Rt, rT, rt Rr Tt First Outer Inner Last RT First Rt Outer rT Inner rt Last

2. Legend Round peas = RR, Rr Wrinkled peas = rr Yellow peas = YY, Yy Green peas = yy

3. RrYy x RrYy rryyrrYyRryyRrYy ry Last rrYyrrYYRrYyRrYY rY Inner RryyRrYyRRyy RRYy Ry Outer RrYyRrYYRRYyRRYY RY First ry Last rY Inner Ry Outer RY First

4. Phenotype for a cross involving two parents that are heterozygous for both traits? –9/16 Round,Yellow peas –3/16 Round, Green peas –3/16 Wrinkled, Yellow peas –1/16 Wrinkled, Green peas (56%) (19%) (6%) Ratio - 9:3:3:1

5. Return to Genetics pwpt.