In polygenic traits, what pattern of inheritance leads to a continuous distribution of phenotypes, such as height?

In polygenic traits, what pattern of inheritance leads to a continuous distribution of phenotypes, such as height?

• A. Monogenic inheritance
• B. Epistasis
• C. Incomplete dominance
• D. Polygenic inheritance with additive effects

Answer: (D)

Many traits such as height vary continuously because they are controlled by many genes, each contributing a small amount. When these small effects add up across a large number of loci, the phenotype becomes the sum of those contributions. This additive polygenic model produces a spectrum of phenotypes rather than discrete categories, and environmental influences add further random variation, often shaping the distribution into a bell-shaped curve in the population. In contrast, a single-gene pattern would yield distinct categories, and non-additive interactions at a few loci don’t produce the same smooth, widespread variation seen with height.

Many traits such as height vary continuously because they are controlled by many genes, each contributing a small amount. When these small effects add up across a large number of loci, the phenotype becomes the sum of those contributions. This additive polygenic model produces a spectrum of phenotypes rather than discrete categories, and environmental influences add further random variation, often shaping the distribution into a bell-shaped curve in the population. In contrast, a single-gene pattern would yield distinct categories, and non-additive interactions at a few loci don’t produce the same smooth, widespread variation seen with height.