Answer:
one of the examples is 'variation in skin color in humans.
Step-by-step explanation:
Wide variation in skin colour is one of the examples of a polygenic trait. It occurs when a trait is controlled by more than one gene. In such inheritance pattern each dominant allele improves the expression of the next dominant allele. In this example skin colour in humans is determined by three genes. Let’s assume three dominant genes are D, E and F. These dominant genes responsible for dark pigmentation because more melanin is produced. The d, e and f are recessive alleles the control light pigmentation as they produce less amounts of melanin. Each dominant gene produces one unit of color, thus a wide range of intermediate skin colours are produced.