You have identified two mutant lines of corn that each grow in the presence of a

Question

You have identified two mutant lines of corn that each grow in the presence of a particular herbicide. Line 1 is homozygous for recessive mutation a, and Line 2 is homozygous for recessive mutation b. You mate these two lines together to create a hybrid Aa,Bb plant. You want to self this plant to create a new line that will be resistant to both herbicides.

a. If A and B assort independently, what proportion of the F2s would you expect to be able to grow in the presence of both herbicides?

b. Instead, when you grow the F2 seeds in the presence of both herbicides, you find that only 1% grow. Based on these data, how closely linked are A and B?

Explanation / Answer

a. If the A and B assort independently then the ratio of plants that can grow in presence of both herbicides will be 16:1

As the herbicide resistance is a recessive mutation, the plant which show resistance to both herbicides will have the genotype aabb. When you perform the cross between Aa and Bb you will get the ratio 1:1:1:1. (AB, Ab, aB, ab).This is our F1. After selfing ( allow these genotypes to cross over within themselves) , you will get a progeny in which there is only one aabb genotype is formed, that will show resistance to both herbicides.

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