DIHYBRID CROSSES

1. DIHYBRID CROSSES PRINCIPLE OF INDEPENDENT ASSORTMENT

2. Dihybrid crosses are those where we consider the inheritance of two characteristics at the same time.

3. Occurs during gamete formation in meiosis. • Principle of segregation. • Principle of Independent Assortment.

4. There are four possible combinations of the two characteristics. Peas can be: • 1) round and yellow • 2) round and green • 3) wrinkled and yellow • 4) wrinkled and green

5. X Phenotype Round, yellow Wrinkled, green rryy RRYY Genotype all RY all ry Gametes all RrYy F1 All of the F1 generation would be heterozygous for both characteristics, meaning that they would all be round and yellow. As with monohybrid crosses, he then crossed two of the F1 generation together…

6. To determine possible gamete combinations, use the FOIL method (First, Outside, Inside, Last) TtPp First – TP Outside – Tp Inside – tP Last - tp Dihybrid Crosses T t P p

7. X Phenotype Round, yellow Round, yellow RrYy RrYy Genotype RY, Ry, rY, ry RY, Ry, rY, ry Gametes F2 We really need a punnet square for this…

9. F2 : : : 9 3 3 1 Round Yellow Round Green Wrinkled Yellow Wrinkled Green This is the typical ratio expected in a dihybrid cross.

10. Mendel formulated the Law of Independent Assortment to explain that two traits are inherited independently of each other.

11. Dihybrid cross