# What is the Difference Between Complete and Incomplete Dominance

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 Complete Dominance Incomplete Dominance F1 is similar to dominant parent. F1 is different from either of the two parents. Phenotypic ratio = 3 : 1 Phenotypic ratio = 1 : 2 : 1 Genotypic ratio = 1 : 2 : 1 Phenotypic ratio ≠ Genotypic ratio Phenotypic ratio = Genotypic ratio In F1 dominant trait expresses fully In F1 dominant trait is incompletely expressed One dominant allele is enough to express dominant trait Two alleles are required to fully express dominant trait Examples: Humans (Hairy is dominant over Baldness); Blood group Allele A is dominant over blood group O Examples: Mirabilis Jalapa; Snapdragon - Antirrhinum Majus

## Gene Interactions

Both the Complete and Incomplete Dominance are the Intragenic (Allelic) Gene Interaction. The other types are:
• Intragenic (Allelic) Gene Interaction
• Intergenic (Non-Allelic) Gene Interaction
• Epistasis
• Duplicate Genes
• Complementary Genes
• Supplementary Genes
• Polymeric Genes
• Pleiotropy
• Polygenic Genes

## Incomplete Dominance

In the case of Incomplete Dominance, dominant allele do not completely express itself, resulting in a different phenotype. F1 generation expresses a phenotype which is intermediate between those of the parent.

Carl Correns discovered incomplete dominance and cytoplasmic dominance.

## Definition of Incomplete Dominance

Incomplete dominance is a type of Gene interaction, in which, in a heterozygous condition, both alleles of a gene at a locus are partially expressed, often resulting in an intermediate (or different) phenotype. It is also called partial dominance.

## Complete Dominance

In the case of Complete Dominance, dominant allele completely express itself, thereby masking the effect of Recessive allele, resulting in a dominant phenotype. F1 generation expresses a phenotype which is dominant between the parents.

## Definition of Complete Dominance

Complete dominance is a type of Gene interaction, in which, in a heterozygous condition, the dominant allele of a gene at a locus is fully expressed, supressing the recessive allele, resulting in a dominant phenotype.

## Multiple Choice Questions

In F2 generation, we observe the phenotypic ratio = 3 : 1. Which of the following conclusion would be correct?
(1) Trait = 2, Dominance = Complete
(2) Trait = 1, Dominance = Incomplete
(3) Trait = 1, Dominance = Complete
(4) Trait = 2, Dominance = Incomplete

Ans: http://zoomgenetics.apphb.com/?id=m39


In F2 generation, we observe the phenotypic ratio = 1 : 2 : 1. Which of the following conclusion would be correct?
(1) Trait = 2, Dominance = Complete
(2) Trait = 1, Dominance = Incomplete
(3) Trait = 1, Dominance = Complete
(4) Trait = 2, Dominance = Incomplete

Ans: http://zoomgenetics.apphb.com/?id=m40


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