In this video, we're going to introduce codominance. Codominance is a pattern of inheritance where heterozygotes with two different alleles equally express both phenotypes from each allele in patches. In other words, codominance is when two different alleles dominate together. When you take a look at the word codominance, the root 'co' in front of dominance is a root that means together, just like 'cooperate' has the root 'co' which means together. Codominance means that they're going to dominate together, where one allele does not mask the expression of the other allele. Instead, they dominate together. We're going to take a look at an example of codominance in red and white flowers, which is very similar to our last example in our last lesson video, except instead of showing an incomplete dominance pattern of inheritance, here we're showing a codominance pattern of inheritance.
Once again, we're taking a look at these two different alleles, the r1 allele, which is associated with a red flower phenotype, and the r2 allele, which is associated with a white flower phenotype. When we cross a homozygous red flower with two r1 alleles and a homozygous white flower with two r2 alleles, we're going to get this Punnett square that we see here where we get r1 and r2 heterozygotes as the offspring, just like what we saw in our last lesson video. But the difference was that with incomplete dominance in our last lesson video, the heterozygotes would create some kind of blended intermediate phenotype that did not really exist in either of the parents.
However, here with codominance, there's no blended intermediate phenotype. There are no pink flowers. Instead, with codominance, both phenotypes are going to be equally expressed. You see patches of white flower down below and you also see patches of red flower. The white and red portions of this flower are expressed equally in patches, and that is what codominance is all about. This is in heterozygotes that have one r1 and one r2 allele. This here helps you better distinguish between incomplete dominance and codominance. In our next lesson video, we're going to introduce one of the most common examples of codominance, which is blood type. So, I'll see you all in that video.
