How are quantitative traits related to polygenic inheritance?

• A. They are traits controlled by a single gene
• B. They exhibit a narrow range of phenotypes
• C. They are determined by multiple genes and show variation
• D. They occur only in complex organisms

Answer: (C)

Quantitative traits are indeed determined by multiple genes, which contributes to the variation observed in their phenotypes. These traits do not follow the simple Mendelian inheritance patterns, where a single gene dictates a phenotype, but rather involve the cumulative effects of several genes, often referred to as polygenes. Each of these genes may have a small additive effect on the trait's expression, leading to a continuous range of phenotypes.

This polygenic nature is what results in traits like height, skin color, or grain weight in plants, where individuals display a spectrum of characteristics rather than distinct categories. The presence of multiple alleles at multiple loci allows for the intricate blend of characteristics observed in populations, which is characteristic of quantitative traits. This complexity and resultant variability are hallmarks of polygenic inheritance, connecting the principles of genetics to observable traits within organisms.