Question

The allelic combination of the variety 1 is AAbbCCddEE and has the phenotype of 6 yield units. The allelic combination of variety 2 is aaBBccDDe and has 4 yield units. What would be the yield unit and heterosis (over the better parent) unit of the F1 (if there is complete dominance)?

• A. 6 and 4
• B. 10 and 6
• C. 10 and 4
• D. 4 and 4

Hint:

Heterosis (Hybrid vigour):
- F1 > Better parent.
- Heterosis unit = F1 - Better parent.
- Complete dominance results in all dominant alleles expressed.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
This question tests knowledge of additive gene action and heterosis.

Step 2: Key Formula or Approach:
Under complete dominance, the F1 will express all dominant alleles.
Heterosis (better parent heterosis) = (F1 - Better parent) Better parent × 100.
But here, heterosis is given in units.

Step 3: Detailed Explanation:
Variety 1: AAbbCCddEE (6 units).
Variety 2: aaBBccDDe (4 units).
F1: AaBbCcDdEe (since E from variety 1, e from variety 2).
Under complete dominance, the F1 will have all dominant alleles expressed.
The F1 will have:
- From variety 1: A (dominant), C (dominant), E (dominant).
- From variety 2: B (dominant), D (dominant).
Yield units: A, B, C, D, E each contribute?
Variety 1 has 6 units (A, C, E contribute, and b, d, d are recessive).
Variety 2 has 4 units (B, D contribute, and a, c, c are recessive).
Total units in F1 = 6 + 4 = 10 (all dominant alleles expressed).
Heterosis over better parent = F1 - Better parent = 10 - 6 = 4 units.
Thus, yield unit = 10, heterosis unit = 4.

Step 4: Final Answer:
Thus, the yield unit is 10 and heterosis unit is 4, which corresponds to option (C).
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