Final answer:
Body weight in humans is a polygenic trait, meaning it is influenced by multiple genes, each with multiple possible alleles, resulting in a wide range of phenotypes.
Step-by-step explanation:
Body weight is a continuous trait in humans, which means it is polygenic. This indicates that body weight is controlled by more than one gene, and each gene may have multiple alleles. In polygenic inheritance, traits exhibit a wide range of phenotypes with many possible appearances.
For example, skin color, height, and body weight are all polygenic traits. These traits can be measured and typically show a bell-shaped curve of distribution in a population, with most individuals falling in the middle of the phenotypic range and fewer at the extremes. For instance, individuals who are dominant for all height alleles would be very tall, while individuals who are recessive for all the alleles would be shorter. Those in the middle will have a mix of dominant and recessive alleles.