Final answer:
Polygenic inheritance is the concept that multiple genes contribute to a single phenotype in a cumulative manner, affecting traits such as skin color and eye color, which are examples of polygenic traits with significant genetic and environmental influences.
Step-by-step explanation:
The polygenic inheritance hypothesis suggests that many factors or genes contribute to the phenotype in a cumulative or quantitative manner. Unlike Mendel's initial thoughts on inheritance which focused on single-gene traits, characteristics such as human skin color, height, and eye color are influenced by the interaction of multiple genes. For instance, it is now known that at least three genes are involved in determining skin color, and more than eight genes contribute to eye color in humans. This complexity extends further as genes can be expressed sequentially in organ development, function in complementary or synergistic ways, or even oppose each other's effects.
Polygenic traits can generally be measured and display a wide range of variability influenced by genetics and environment, which is vital for the survival and adaptation of species. Understanding the polygenic basis of traits provides valuable insights into predicting traits in offspring and assessing the risk for heritable genetic disorders, although most diseases have a multigenic pattern of inheritance influenced also by environmental factor