List two human traits that show variations.

Hint: Polygenic inheritance controls multiple genes which lead to the formation of intermediate heritable characters. Polygenic traits result in continuous variation by which offspring differ from their parents.

Complete Answer:
Humans show many polygenic traits, human height, and skin color are two human traits that show variations.
697 genetic variants cause different heights in humans like small, tall, and intermediate. The height of a person is the result of parent gene combination, it is not necessary that parents with tall height result in children of tall height. Not only genes determine the height of a person, hormones and nutrition also play a major role which results in variations in height.
Skin color depends upon the gene and the melanin pigment production, the maximum production of melanin pigment results in dark color while minimum production results in a light color.
Hair color and eye color are also an example of a polygenic trait in humans, in this variation also depends on the production of melanin but discoloration. Polygenic traits are not only shown by humans but some animals also show variation in skin color for example rabbits, mice, etc.
Polygenic inheritance results in a bell-shaped graph because the dominant and recessive character is shown by less number of people while the intermediate character is shown by a large number of people. The frequencies of polygenic characters follow a continuous range of variation. Polygenic inheritance determined by variances, covariance, and average. Polygene allows a large number of possibilities in polygenic traits.

Note: Polygenes also cause genetic disorders like type-2 diabetes, coronary heart disease, cancer, hypertension, and mental illness. Disease transfer from generation to generation by gene inheritance.