Homozygous Phenotypes

The concept of “blending” as championed by such scholars as Aristotle and Hippocrates states that any trait that an offspring receives is the average of both of its parents. This concept was widely believed until Mendel’s experiments. Incomplete dominance occurs when the heterozygous phenotype is an intermediate between both of the homozygous genotypes. This concept is demonstrated best through the inheritance of petal color in a snapdragon. In a heterozygote the phenotype would be pink, a mix between the homozygous genotypes of red and white. This happens because neither allele is dominant, so the colors are expressed together. This concept is similar to the idea of “blending” that many previous scientists believed. When examining this concept, it is easy to see how Aristotle and Hippocrates came to support “blending”. …show more content…
In individuals with heterozygous alleles, both of the traits appear together in the creation of a third phenotype. In the case of the snapdragon, codominant inheritance would cause the flower to have blotches of each of the colors, thus appearing spotted. The idea of codominance, while very similar to incomplete dominance, might have played a lesser role in the development of the incorrect concept of “blending”. Epistasis has nothing to do with the genotype of an individual, but it does affect how certain traits are expressed. Epistatic genes modify the phenotypic expression of other genes by masking the phenotype of the other gene’s alleles. An example of epistasis can be seen in the inheritance of fruit color in Summer squash. One gene codes for a white color and the other for green/yellow color. Whenever a dominant allele from the white-coding gene is present, the white masks the other colors. This concept could have caused some confusion that might have led past philosophers to come up with the idea of