The fruit in summer squash may have different shapes. When two true breeding plants with disc-shaped fruit were crossed to true breeding plants with long fruit, all the F1 plants had disc fruits. In the F2 progeny there were 110 plants with disc-shape fruits, 70 plants with sphere-shape fruits and 12 plants with long fruits.

How many genes are involved in determination of fruit shape in summer squash?

b)propose a model that would explain the observed pattern of inheritance. Assign genotypes to the parents, F1 and F2 progeny that would explain the observed ratios.

c)use chi square analysis to test your model.

d) how coul you explain this inheritance at the molecular level?