Dominance


 * DOMINANCE TYPES AND DESCRIPTIONS **

Complete dominance is the type of dominance in which the allele which is dominant rules completely. The difference between a hybrid and a true breed would be completely unnoticeable without looking at it from a molecular level. This dominant allele will be expressed no matter where it is placed. For example, if you have two parents, one with blue eyes and the other with brown, brown being the dominant allele, if it's complete dominance, the offspring's eyes would be a solid brown. Notice how the blue allele, even if the baby does contain Bb, is not expressed or emphasized. However, it might show if two hybrids are crossed, if even if both contain brown as their dominant eye color, for hybrids have multiple possibilities of outcome when crossed. Incomplete dominance is the type of dominance in which neither allele really dominates more than another. So, instead of ruling over one another, they practically combine to form something in between. Sticking to the same theme about the eye color, imagine that these parents were pure breeded of different phenotypes. (Mom=blue eyed and Dad=brown eyed). When crossed, there is 100% chance for BOTH to have complete dominance over each other. However, this cannot happen. What may happen is incomplete dominance, in the case that they refuse to codominate. They could combine their phenotypes (blue and brown) to create a blend of both, which would be a darkish gray color. This is incomplete dominance. Neither is ruling over each other or together, but created a whole different scenario in which they created somethign new. In this case, it may physically appear that the current color being shown, rather, reflected, is the allele with the complete dominance. However, if you look deeper into its genetic history, you will see that it was not the complete dominance of the gray allele, but the incomplete dominance of brown and blue.

Codominance is the type of dominance in which BOTH alleles are expressed. How does this work? Well, let's continue with the eyes. Mom has blue eyes and dad has brown eyes. Let's say that they are equally dominant, but refuse to participate in incomplete dominance. In this case, you may have an offspring with one eye blue and the other brown. The same case goes to flowers, the most common in which it appears. If the mom is red and the dad is white, and they both speak just as loud, the offspring would have a combination of both colors. May it be different colored petals or just freckled red and solid white. Whatever the case may be, they do not mix or create something new, but instead exist in the offspring codominating. However, it is similar to incomplete dominance in the sense that they both do not have an allele that dominates completely over one another.

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