Partial Dominance
There are certain characteristics whose expression cannot be fully explained by the pure dominant/recessive way of thinking. Thus to explain certain phenotypes, we use the terms Partial Dominance, or Intermediate Inheritance. In this, no trait is fully dominant over another; so a mixing of a characteristic is formed. There are two main manifestations of this: Incomplete dominance and Codominance.
1. Incomplete Dominance: In Incomplete Dominance, genes are designated by two capital letters. This type of partial dominance is a midway between two extremes; most often between colors of an organism. In the flowers of the Japanese four-o’clock and the Snapdragon, a red flower has a genotype of RR and a white one has a genotype of WW.
			R			R
	W		RW			RW
	W		RW			RW
When crossed, there is a 100% chance that the offspring will be a RW heterozygous flower, with a phenotype showing light pink flowers. When two heterozygous flowers have offspring, there is a 25% chance it will be red, 50% chance it will be pink, and 25 % chance it will be white.
			R				W
	R		RR				RW
	W		RW				WW
The other common example of Incomplete dominance is the Andalusian foul. In this animal, the color of the homozygous is black and white. When mated, the heterozygous is blue.
2. Codominance: In Codominance, the phenotype is not an expression of a different median between the two traits, as it is in Incomplete Dominance. Here it is a partial representation of both. In the shorthorn cattle, the homozygous red and white hairs are denoted as C^R C^Rand C^W C^W, respectively. The superscript letters show that it is Codominance. When these mate, there is a 100% chance of offspring with a roan coat; that is, a coat with both red and white hairs.
				C^R	C^R
		C^W		C^R C^W	C^R C^W
		C^W		C^R C^W	C^R C^W
As would be expected, when two roan coated shorthorn cattle mate, their offspring will have a 25% chance of being red or white, and 50% chance of being roan coated. Take a Quiz on this