Question

Continuous variations because of additive effects of two or more genes for a trait is:

• A. Complementarity
• B. Epistasis
• C. Dominant
• D. Polygenic

Hint:

Quantitative traits that show continuous variation in a population are controlled by polygenes, where each gene has an additive effect on the phenotype.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
In genetics, phenotypic traits can be classified as qualitative (discontinuous variation) or quantitative (continuous variation).
Continuous variation is typically governed by multiple genes acting cumulatively.

Step 2: Detailed Explanation:
Let us evaluate the genetic terms listed:
1. Complementarity (A): A type of gene interaction where two non-allelic genes must both be present to produce a specific phenotype.
This interaction produces distinct, discontinuous phenotypic classes.
2. Epistasis (B): A gene interaction where one gene masks or modifies the phenotypic expression of another gene at a different locus.
This also produces distinct, discontinuous classes.
3. Dominance (C): An allelic interaction where one allele at a locus masks the expression of the other allele.
4. Polygenic Inheritance (D): Also known as quantitative inheritance, this occurs when a single phenotypic trait is controlled by the additive effects of two or more independent genes.
Each gene contributes a small, cumulative effect to the final phenotype.
This additive gene action, combined with environmental factors, results in continuous variation across a population (producing a bell-shaped normal distribution curve).
Examples include plant height, kernel color in wheat, and yield parameters.

Step 3: Final Answer:
Therefore, continuous variation resulting from the additive effects of multiple genes is polygenic inheritance.