Define/Explain: Polygenic Inheritance.

The grain color in wheat is controlled by three pairs of polygenes. When a red-grained wheat variety is crossed with a white-grained variety,an $F_1$ hybrid is produced. When the $F_1$ hybrid is self-pollinated,what fraction of the $F_2$ generation will resemble the parental phenotypes?

In a case of polygenic inheritance,a trait is controlled by $3$ pairs of genes. If an individual is heterozygous for all $3$ alleles,what will be the phenotypic ratio produced by self-crossing?

In a polygenic trait,an individual with three recessive alleles expresses $50 \%$ of the trait,while an individual with three dominant alleles expresses $80 \%$ of the trait. What is the contribution of each dominant allele to the trait (in $\%$)?

The inheritance of skin color in humans is an example of which of the following?

An example of a quantitative trait in humans is .....