Consider two unlinked genes P and Q. A plant with genotype PPQQ was crossed with another plant with genotype ppqq to obtain F1 progeny. If the F1 progeny is test-crossed, the percentage of resultant plants with the genotype ppqq will be.
A
50%
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B
25%
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C
100%
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D
10%
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Solution
The correct option is B25%
The cross can be described as shown in the figure.
When F1 progeny is test crossed (test cross is the cross with homozygous recessive parent), the resultant phenotypes are PpQq, Ppqq, ppQq, ppqq in the ratio 1:1:1:1.
Hence, percentage of plants with genotype ppqq = 1/4 x 100 = 25%