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Dihybrid Crosses: Setting Up Punnett Square. Last. First. 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 ( F irst, O uter, I nner & L ast)
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Dihybrid Crosses: Setting Up Punnett Square Last First • 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 Outer Inner RT First Rt Outer rT Inner rt Last
Legend Round peas = RR, Rr Wrinkled peas = rr Yellow peas = YY, Yy Green peas = yy
RrYy x RrYy RY First Ry Outer rY Inner ry Last RY First RRYY RRYy RrYY RrYy Ry Outer RRyy RrYy Rryy RRYy rY Inner RrYY RrYy rrYY rrYy ry Last RrYy Rryy rrYy rryy
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%) (19%) • (6%) Ratio - 9:3:3:1
