Question:
The loci without ___________________ cause neither inbreeding depression nor heterosis.
The loci without ___________________ cause neither inbreeding depression nor heterosis.
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Both heterosis and inbreeding depression are driven by non-additive gene action, specifically directional dominance (\(d \neq 0\)). Purely additive genes show zero heterosis.
Updated On: Jul 8, 2026
- Additive effect
- Epistatsis
- Dominance
- Non-additive effect
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The Correct Option is C
Solution and Explanation
Step 1: Understanding the Concept:
Heterosis (hybrid vigor) and inbreeding depression are genetically related phenomena, both depending heavily on dominance effects.
Step 3: Detailed Explanation:
From quantitative genetics, we know that the change in mean due to inbreeding (\(\Delta M\)) is:
\[ \Delta M = -2 \sum d_i p_i q_i F \]
where \(d_i\) is the dominance deviation at the \(i\)-th locus.
If a locus has no dominance (i.e., it has only additive gene action, \(d = 0\)), then:
\[ -2 (0) p_i q_i F = 0 \]
This means that loci with only additive genetic effects do not exhibit any change in mean under inbreeding (no inbreeding depression) or crossbreeding (no heterosis).
Thus, dominance is an absolute prerequisite for these phenomena.
Step 4: Final Answer
Loci without dominance cause neither inbreeding depression nor heterosis.
Heterosis (hybrid vigor) and inbreeding depression are genetically related phenomena, both depending heavily on dominance effects.
Step 3: Detailed Explanation:
From quantitative genetics, we know that the change in mean due to inbreeding (\(\Delta M\)) is:
\[ \Delta M = -2 \sum d_i p_i q_i F \]
where \(d_i\) is the dominance deviation at the \(i\)-th locus.
If a locus has no dominance (i.e., it has only additive gene action, \(d = 0\)), then:
\[ -2 (0) p_i q_i F = 0 \]
This means that loci with only additive genetic effects do not exhibit any change in mean under inbreeding (no inbreeding depression) or crossbreeding (no heterosis).
Thus, dominance is an absolute prerequisite for these phenomena.
Step 4: Final Answer
Loci without dominance cause neither inbreeding depression nor heterosis.
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