Question

Consider two unlinked genes P and Q. A plant with genotype PPQQ was crossed with another plant with genotype ppqq to obtain $F_1$ progeny. If the $F_1$ progeny is test-crossed, the percentage of resultant plants with the genotype ppqq will be.

• A. $50\%$
• B. $25\%$
• C. $100\%$
• D. $10\%$

Answer 1

The correct option is B $25\%$

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%

So, the correct answer is B.