Dominant genes
Recessive genes
Multiple genes
Mutated genes
A polygenic pattern is a type of inheritance pattern where one trait is controlled by multiple genes. Each gene has multiple alleles and creates a continuous pattern of expression with many phenotypes.
- In polygenic inheritance, each allele has a cumulative or additive effect on the phenotype thus generating continuous variation, e.g. skin pigmentation, height, etc.
- Three examples of polygenic traits in humans are height, skin colour and eye colour. These traits are governed by multiple genes.
- ABO blood type is an example of multiple allelism, where a single gene has three different alleles or variants (in the same locus) and an individual contains any of the two alleles. It is different from polygenic inheritance. Gene I has 3 alleles IA, IB and i. The combination of two allele pair decides the blood type.
- Eye colour is a polygenic trait. There are two major eye colour genes, OCA2 and HERC2, which are present on chromosome 15. Other than these, there are more than 13 genes identified that determine the expression of the phenotype (colour of eye). At least 9 colours of eye are recognised in humans.
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