Provide a definition and an example for each of the following terms:
Polygenic inheritance

Verified step by step guidance

1. Polygenic inheritance refers to a type of genetic inheritance where a single trait is controlled by two or more genes, often located on different chromosomes. These genes contribute to the phenotype in an additive or interactive manner, resulting in a continuous range of phenotypes rather than discrete categories.
2. An example of polygenic inheritance is human skin color. Skin color is determined by the interaction of multiple genes, each contributing to the amount of melanin produced. The combined effect of these genes results in a wide spectrum of skin tones.
3. To understand polygenic inheritance, consider that each gene involved may have two or more alleles, and the cumulative effect of these alleles determines the phenotype. For instance, alleles that promote higher melanin production will add to the overall pigmentation.
4. Polygenic traits often exhibit a bell-shaped distribution in a population, as seen in traits like height, where most individuals fall near the average, with fewer individuals at the extremes.
5. In summary, polygenic inheritance involves multiple genes contributing to a single trait, leading to continuous variation. This is distinct from Mendelian inheritance, where traits are typically determined by a single gene with clear dominant and recessive alleles.

Key Concepts

Polygenic Inheritance

Polygenic inheritance refers to the genetic mechanism where multiple genes (often located on different chromosomes) contribute to a single trait. This results in a continuous range of phenotypes, rather than discrete categories. For example, human height is influenced by several genes, leading to a wide variety of heights in the population.

Quantitative Traits

Quantitative traits are characteristics that are influenced by multiple genes and can be measured on a continuous scale. These traits often show a normal distribution in a population due to the additive effects of alleles. Examples include traits like weight, skin color, and intelligence, which are not simply 'present' or 'absent' but vary in degree.

Environmental Influence

Environmental influence refers to the impact of external factors on the expression of genetic traits. In polygenic inheritance, the phenotype can be significantly affected by environmental conditions such as nutrition, climate, and lifestyle. For instance, two individuals with the same genetic predisposition for height may end up differing in height due to variations in their nutrition during growth.