GENE ACTION
Gene action refers to the way in which genes exert their effects on the body. They could be dominant or recessive. Gene actions results in observable phenotype of an organism. Different types of gene action are as follows:
There are three types of gene action:
1. Additive gene action
Additive gene action states that one allele of gene is substituted by other allele and it produces the same effect whether positive or negative.
2. Dominant gene action
Three types are complete dominance, incomplete dominance and co-dominance
Complete dominance
When a dominant gene (A) is substituted via a recessive gene (a) and there’s no effect. This is called complete dominance. Homozygous (AA) dominant and heterozygous (Aa) dominant are equal.
Incomplete dominance
It is type of gene action in which blending of homozygous and heterozygous allele occurs. Example: Pink flower(Rr) results by blending red (RR) and white flowers (rr).
Codominance
When both alleles expressed. Example ABO blood group
3. Epistatic gene action
In this sort of gene action, the presence or absence of an allele in one locus have an effect on the expression on any other allele in another locus. Epistasis can both exert additive effect or dominance.
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