what are the differences between multiple alleles and polygenic inheritance???
Multiple alleles and polygenic inheritance are two mechanisms of genetic inheritance that contribute to the overall variation observed in traits. Let's understand the differences between them:
1. Multiple Alleles:
- Definition: In a population, multiple alleles are alternative forms of a gene that exist at the same locus (position) on homologous chromosomes.
- Inheritance: In multiple alleles, each individual can have a maximum of two alleles, one on each homologous chromosome. However, the population as a whole may possess more than two alleles for a particular gene.
- Examples: The classic example of multiple alleles is the ABO blood group system, which involves three alleles dominating the population - A, B, and O.
- Expression: A gene with multiple alleles may exhibit co-dominance or complete dominance. For example, in the ABO blood group system, A and B alleles are co-dominant, while the O allele is recessive to both A and B alleles.
2. Polygenic Inheritance:
- Definition: Polygenic inheritance occurs when a trait is controlled by the interaction of multiple genes, each having a small cumulative effect.
- Inheritance: Unlike multiple alleles, where a single gene has multiple variants, polygenic inheritance involves multiple genes. Each gene may have only two alleles.
- Examples: Height, skin color, and eye color are examples of polygenic traits in humans.
- Expression: In polygenic inheritance, the phenotype is a result of the combined effect of multiple genes. The trait often displays a continuous range of variation, rather than discrete categories.
To determine the differences between multiple alleles and polygenic inheritance, it is important to focus on the level at which variations occur. Multiple alleles involve variations within a single gene, whereas polygenic inheritance involves variations across multiple genes. Furthermore, multiple alleles typically show discrete phenotypes, while polygenic traits exhibit continuous variation.