Gene Action in Polygenic Inheritance
Polygenic inheritance is governed by:
- Epistasis
- Over-dominance
- Dominance
- Additive gene action — Correct Answer
Explanation:
Correct Answer: Additive gene action
Polygenic inheritance involves multiple genes each contributing small, equal, and cumulative effects to a single quantitative trait (e.g., milk yield, body weight, egg production). This cumulative effect is governed by additive gene action (AGA).
Types of Gene Action
| Type | Sub-type | Example |
|---|---|---|
| Additive Gene Action (AGA) | Polygenic traits | Body weight, milk yield, fleece weight |
| Non-additive Gene Action (NAGA) | Allelic interaction (Dominance, Over-dominance, Incomplete dominance) | Coat colour, heterosis |
| Non-allelic interaction (Epistasis) | Coat colour ratios, combs in poultry |
Importance of Additive Gene Action
- Heritability (h²N) = VA/VP — where VA is additive genetic variance — meaning additive gene action is directly captured by narrow-sense heritability.
- Heterosis depends on non-additive gene action; traits with low h² show high heterosis.
- Additive effects are fixable by selection; non-additive effects are not.
📚 About this Topic — Animal Genetics & Breeding
This multiple choice question is from Animal Genetics & Breeding, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Genetics & Breeding to strengthen your preparation.
