Question

Match LIST-I with LIST-II

Choose the correct answer from the options given below:

• A. A-I, B-II, C - III, D - IV
• B. A-II, B-I, C - IV, D - III
• C. A-IV, B - III, C - II, D-I
• D. A-III, B - IV, C - I, D - II

Hint:

To quickly recall these ratios, remember the totals. Complementary (9+7=16), Recessive Epistasis (9+3+4=16), Dominant Epistasis (12+3+1=16), and Inhibitory (13+3=16). Associate Complementary with 9:7 and Dominant Epistasis with 12:3:1 as the most common examples.

Answer 1

The Correct Option is C

Step 1: Concept Overview:
This question assesses understanding of gene interactions (epistasis) and their modified Mendelian F2 dihybrid ratios. The standard dihybrid ratio is 9:3:3:1.
Step 2: Detailed Explanation:
Matching each gene interaction type with its F2 ratio:


A. Complementary gene action: Both dominant genes (e.g., A and B) are needed for a specific phenotype. Absence of either results in a different phenotype. A_B_ gives one phenotype; A_bb, aaB_, and aabb give another, combining the 3, 3, and 1 portions for a 9:7 ratio. This corresponds to IV.

B. Supplementary gene action (Recessive Epistasis): A recessive allele (e.g., aa) at one locus masks alleles at another. A_B_ (phenotype 1), A_bb (phenotype 2), but aaB_ and aabb (phenotype 3). This combines the 3 and 1 portions, resulting in a 9:3:4 ratio, matching III.

C. Inhibitory gene action: A dominant allele (inhibitor gene, I) at one locus prevents expression at another. I_C_ and I_cc yield one phenotype (e.g., white), iiC_ a second (colored), and iicc the first again (white). Combining the 9, 3, and 1 portions gives a 13:3 ratio, corresponding to II.

D. Masking gene action (Dominant Epistasis): A dominant allele (e.g., A) at one locus masks alleles at another. A_B_ and A_bb give one phenotype, aaB_ a second, and aabb a third. Combining the 9 and 3 portions leads to a 12:3:1 ratio, matching I.

Step 3: Final Answer:
The correct match is A-IV, B-III, C-II, D-I.