Note that all these alleles are found in the same position on the chromosomes. In this way, with multiple alleles, more than just two or three phenotypes can be seen. The allele that produces A antigens is, or i. Since the person with type AB blood produces both antigens, it is codominant, where both the genes are expressed. A person with type A blood only has the A antigens, B blood only has the B antigens, a person with type AB blood has both, and a person with type O blood does not have either of the antigens. They can be arranged to produce four different blood types: A, B, AB, and O. There are two types of antigens, A and B. Red blood cells in humans have specific antigens on their surface. One example of another trait that shows codominance is human blood type. If this chicken was mated with another similar one, the offspring would be 1 brown: 2 specked: 1 white.

The Punnett square for codominance and the genotype and phenotype ratios for codominance is the same as for incomplete dominance. The image below shows a speckled chicken. In both of these cases, both alleles in the heterozygote are expressed. Some other examples are seen with speckled chickens, which have both black and white feathers due to codominance, or roan cattle with both red hair and white hair. In plants, it may be seen as a plant with red and white spots of color when the genotype is heterozygous. With codominance, both genes are expressed, so instead of blending, they will both be seen. In Incomplete Dominance, the heterozygous individuals have a trait between the two original characteristics, such as the snapdragons in which a red and white snapdragon will produce a pink one. How does Incomplete Dominance differ from Codominance? Another example can be seen with codominance. Incomplete dominance is one example of when a trait does not show complete dominance. The red ones have two red alleles, the pink ones have one red and one white allele, and the white ones have two white alleles.ĭifference Between Incomplete Dominance and Codominance Then if two individuals from the F1 generation are crossed, the incomplete dominance genotype will be 1 red (RR): 2 pink (RW): 1 white (WW). Individuals who are heterozygous produce a color that blends the two colors.

In this case, there are no recessive or dominant traits. When the parental generation of red snapdragons (RR) and white ones (WW) are crossed, the offspring (F1 generation) are all pink (RW). Some traits blend and show incomplete dominance. This white allele was called the recessive allele. The three that had a A (AA and the two Aa) produced purple flowers, and the one that had two white alleles (aa) made white flowers. The genotype (actual alleles) ratio of these offspring was 1:AA:2Aa:1aa. The offspring of such a cross was called the F2 generation, and the ratio of the offspring was three purple flowers for every white flower.

He then crossed two of these heterozygous individuals (Aa). In this case, they have one allele for purple flowers (represented by the 'A' allele in the image) and one for white flowers (represented by the 'a' in the image). The offspring of this cross were heterozygous, which meant that they had one of each allele. He expected to see plants with intermediate flower color, but he did not see this thus, purple was the dominant trait.

He was working with pea plants, and he found that crossing a parental generation with pure breeding purple flowers with a plant that was pure breeding for the white flower gave all purple offspring. Gregor Mendel did early work in genetics, and he discovered this idea of dominance. Alleles are forms of a gene that have a particular trait. The idea of dominance refers to a type of inheritance, where one allele masks or hides the expression of another allele.

Genotypes of dominant traits