Creating models of the processes that occur at the genetic level is a rather tricky process that may trigger convoluted results and even lead to erroneous assumptions. The alleged phenomenon of blending is one of the graphic examples of these misunderstandings. Although supported extensively by Aristotle and Hippocrates, it relies on a false assumption resulting from a misinterpretation of the concepts such as incomplete dominance, co-dominance, epistasis, pleiotropy, and polygenic traits.
The concept of incomplete dominance implies that the zygote has the phenotype that is not only different from the one of the parents but also typically is in the middle between the two as far as the properties are concerned. Seeing that, as a result of incomplete dominance, certain elements of the recessive alleles are not entirely outbalanced by the dominant ones; as a result, the phenotypes of approximately half of the population retain the phenotypic characteristics of the recessive allele.
The phenomenon of co-dominance, in its turn, occurs in case neither of alleles is recessive or dominant. As a result, the phenotype of the zygote incorporates the characteristics of both alleles. Seeing that the phenotype represents not a mixture but a combination of the two, the theory of blending was designed as the tool for explaining the phenomenon.
Similarly, epistasis, which is defined as the ability of a gene belonging to a different allele to affect the presence of a specific gene, may lead to the invalid assumption that blending is a possible tool for explaining the observed phenomenon. In other words, the lack of observation of the effects that the gene suppressing the one from a different allele has on the phenotype of the zygote may cause one to think that the blending theory has a reason to exist. In reality, however, the phenotype of the other gene is locked or masked, whereas one of the first genes is manifested extensively in the second-generation representatives. Without knowing the specifics of the gene that can mask the properties of the other one, the observer may make a false assumption about blending as one of the possible explanations of the fact that ¾ of the next generation have certain characteristics that the epistatic gene predetermined.
Pleiotropy is another example of how a specific phenomenon may be misinterpreted. Similarly to the concept described above, pleiotropy implies that a specific gene may control at least two phenotypic characteristics that may seem completely unrelated to each other. For instance, several hereditary disorders caused by a specific gene can be deemed as an example of pleiotropy. The concept may be viewed mistakenly as the support for the blending theory.
Polygenic traits, or the characteristics that are defined by at least two genes, also used to be viewed as the support for the blending theory since their presence is determined by two or more genes. Therefore, the properties such as skin color, which is affected by a range of genes, may be falsely considered the manifestation of the blending theory.
When misinterpreted, the essential concepts of genetics, such as incomplete dominance, co-dominance, epistasis, pleiotropy, and polygenic traits, may spark the theories that will lead to significant mistakes in interpreting the mechanism of genetics. Despite the fact that the principle of blending is faulty in its nature, it has been supported as a viable theory by Hippocrates and Aristotle. Nevertheless, it is based on an entirely false premise. Applying the blending framework means simplifying a range of genetic processes that need careful observation and detailed analysis.