2. In corn, the phenotype of the kernels is controlled by two genes. One gene de

Question

2. In corn, the phenotype of the kernels is controlled by two genes. One gene determines the smoothness of the kernel with smooth being dominant and shrunken being recessive. The second gene determines the color of the corn kernel with purple being dominant and yellow being recessive. In the P generation, you crossed a true-breeding rple-smooth corn with a true-breeding yellow-shrunken corn. You then allowed self- ertilization of the F1 generation and observed the phenotypes of the F2 generation. The results are below: Observed 402 Phenotype Purple-smooth Purple-wrinkled Yellow-smooth 135 152 Yellow-wrinkled 35 a. What is your hypothesis? b. Based on your observations would you accept your hypothesis? Show all work. c. Why would you accept or reject your hypothesis?

Explanation / Answer

a. In the P generation true breeding is done between two parents. True breeding means that the parents are homozygous(I.e. a pair of identical alleles) for the traits. So in the first parent there are two dominant genes purple and smooth whereas in second parent there are two recessive genes yellow and shrunken.

So in the F1 progeny we get all the corn as purple and smooth because of the dominant genes. But in the F2 progeny most of the plants will be heterozygous dominant. Hence there is a greater number of purple and smooth kernels. And some are heterozygous recessive they are purple and white. And in other kernels both the genes are recessive and expressed in few number. So according to my hypothesis dominant genes are expressed more in any cross than the recessive genes.

b. Yes based on this observation I accept this hypothesis.

If suppose we take dominant genes purple and smooth recessive genes yellow and shrunken. A dihybrid cross is performed between these and the progeny obtained in high number is purple and smooth kernels.

c.I accept the hypothesis because the result shows exactly how the results are obtained when we perform the true breeding and dihybrid crosses between the F1 progeny. And finally the dominant genes are expressed more than the recessive genes. Hence there are about 402 purple and smooth kernels when compared to the other progeny.

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