Explanation of the statement: "Every gene has cumulative effect in polygenic inheritance"

Polygenic inheritance refers to the inheritance of traits that are controlled by multiple genes. These traits may show a wide range of variations in the population, and the contribution of each gene towards the trait is usually small. In such cases, the effect of each gene is said to be cumulative, which means that the more copies of the "good" allele a person has, the more likely they are to express the trait.

Cumulative effect of genes in polygenic inheritance

In polygenic inheritance, the effect of each gene is additive, meaning that the more copies of the "good" allele a person has, the more likely they are to express the trait. For example, height is a polygenic trait that is controlled by multiple genes. The more "tall" alleles a person has, the taller they are likely to be. However, it is important to note that the effect of each gene is small, and the interactions between different genes and environmental factors can also play a role in determining the final phenotype.

Examples of polygenic traits

Polygenic traits are common in humans and other organisms. Some examples of polygenic traits in humans include:

- Skin color
- Eye color
- Hair color and texture
- Height
- Intelligence
- Risk of developing certain diseases (e.g. diabetes, heart disease)

Inheritance patterns of polygenic traits

Polygenic traits do not follow the typical Mendelian inheritance patterns, where the phenotype is determined by the genotype of a single gene. Instead, the traits are influenced by multiple genes, each with a small effect. This makes it difficult to predict the phenotype of offspring based on the genotype of their parents.

Conclusion

In summary, the statement "Every gene has cumulative effect in polygenic inheritance" means that the effect of each gene is additive, and the more copies of the "good" allele a person has, the more likely they are to express the trait. Polygenic traits are common in humans and other organisms, and their inheritance patterns are complex due to the involvement of multiple genes and environmental factors.