A breeder obtains three mutant strains (A, B, and C) of true-breeding, white-flo

Question

A breeder obtains three mutant strains (A, B, and C) of true-breeding, white-flowered sweet peas. Purple is the wild-type flower color. When A and B or B and C are crossed, the F1 are all purple-flowered. When either of these purple F1 are selfed, about 44% of the progeny are white and the rest are purple. When strains A and C are crossed, the F1 are all white. When these white plants are selfed, only 0.010% of the progeny are purple. Explain these data in terms of complementation and intragenic recombination. A breeder obtains three mutant strains (A, B, and C) of true-breeding, white-flowered sweet peas. Purple is the wild-type flower color. When A and B or B and C are crossed, the F1 are all purple-flowered. When either of these purple F1 are selfed, about 44% of the progeny are white and the rest are purple. When strains A and C are crossed, the F1 are all white. When these white plants are selfed, only 0.010% of the progeny are purple. Explain these data in terms of complementation and intragenic recombination. A breeder obtains three mutant strains (A, B, and C) of true-breeding, white-flowered sweet peas. Purple is the wild-type flower color. When A and B or B and C are crossed, the F1 are all purple-flowered. When either of these purple F1 are selfed, about 44% of the progeny are white and the rest are purple. When strains A and C are crossed, the F1 are all white. When these white plants are selfed, only 0.010% of the progeny are purple. Explain these data in terms of complementation and intragenic recombination.

Explanation / Answer

When we cross A (AAbb) and B (aaBB) , purple flowers are obtained (AaBb). This means that A and B are different genes. Similarly when we cross B (BBcc) and C(bbCC), purple flowers(BbCc) are obtained, means that B and C are different genes which complement each other. Crossing A and C, gives all white flowers. This means that A and C are present on the same chromosome. They both are the same genes. And genotype of A and C should be the same. When AaBb are selfed, chances of having A_B_ (purple) are 3/4*3/4 = 9/16 = 56%. So, chances of having white will be 44%. That is totally consistent with the result obtained. Recombination is totally following Mendelian laws. There is no linkage.

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