Question

A plant producing white flower with white seed coat (dominant) was crossed with a plant producing violet flower with gray seed coat (recessive). Upon selfing of 144 F2 progeny plants, the number of plants continuing to produce violet flower with gray seed coat will be:

• A. 72
• B. 36
• C. 18
• D. 9

Hint:

Use Mendelian ratios to predict offspring phenotypes. A cross between two heterozygous F1 plants follows a 9:3:3:1 ratio for dihybrid crosses.

Answer 1

The Correct Option is D

Step 1: Understanding the inheritance of traits.
The plant has two traits: flower color and seed coat color. The white flower (dominant) and white seed coat (dominant) are crossed with violet flower (recessive) and gray seed coat (recessive). The F1 plants will all be heterozygous for both traits.

Step 2: Using Mendelian inheritance for F2 generation.
The selfing of the F1 generation will give a 9:3:3:1 ratio for the four phenotypes. For the specific combination of violet flower and gray seed coat (recessive traits), the probability is \(\frac{1}{16}\). Multiply this by the total number of progeny (144) to find the number of plants with violet flower and gray seed coat:
\[ \frac{1}{16} \times 144 = 9 \]

Step 3: Conclusion.
Thus, the number of plants continuing to produce violet flower with gray seed coat is 36.