How is polygenic inheritance different from Mendelian inheritance?

Polygenic inheritance involves multiple genes influencing a single trait, whereas Mendelian inheritance involves single genes determining single traits.

Polygenic inheritance and Mendelian inheritance are two different ways in which traits are passed down from parents to offspring. In Mendelian inheritance, named after the monk and scientist Gregor Mendel, traits are determined by a single gene. Mendel's experiments with pea plants led to the discovery of this type of inheritance. He found that certain traits, such as flower colour or seed shape, were determined by individual genes, which exist in different versions or 'alleles'. These alleles can be dominant or recessive, and the combination of alleles an organism inherits from its parents determines the traits it will express.

On the other hand, polygenic inheritance involves multiple genes contributing to a single trait. This means that the trait is not determined by a single gene, but by the combined effect of several genes. Traits that are determined by polygenic inheritance include height, skin colour, and eye colour. These traits show a wide range of variation because they are influenced by many genes, each of which can exist in different forms. This results in a continuous range of possible phenotypes, rather than the distinct categories seen in Mendelian inheritance.

In addition, environmental factors can also influence traits determined by polygenic inheritance. For example, a person's height is influenced not only by their genes, but also by factors such as nutrition and health during their growth period. This adds another layer of complexity to polygenic inheritance, making it more difficult to predict the outcome of this type of inheritance compared to Mendelian inheritance.

In summary, while Mendelian inheritance involves single genes determining single traits, polygenic inheritance involves multiple genes influencing a single trait. Polygenic traits often show a wide range of variation and can be influenced by environmental factors, making them more complex than Mendelian traits.