The concept of blending inheritance introduced and supported by such philosophers as Hippocrates and Aristotle was wrong and did not explain how the life really worked. However, some ideas that led to its occurrence are correct – they just have been misinterpreted.
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The model of blending inheritance implies that the offspring gets the traits that equal to the average of the same traits in their parents (Morris et al. 16-2). For instance, if there is a white rabbit and a black rabbit, their offspring will be gray, that is half white and half black.
However, the main drawback of the theory is evident: if it is true, then rare traits will gradually disappear; instead, they reappear again and again. Times passed and in the nineteenth century, Gregor Mendel discovered that not traits, but genes were transmitted from one generation to another (Morris et al. 16-3).
Presently, many valid genetic concepts seem similar to the concept of blending inheritance, and incomplete dominance probably goes first on the list. It says that neither of homozygous genotypes is completely dominant over another, which is why the new phenotype occurs, the intermediate one (F1 generation) (Morris et al. 16-9). That is why incomplete dominance is similar to the concept of blending.
However, it also implies that F2 generation will display both original phenotypes, which is not assumed by the blending model. One more valid genetic concept could have been misinterpreted and lead to the concept of blending. That is codominance. It says that the offspring receives an allele from each of the parents, and that is how it can be similar to the blending inheritance model. However, it implies that the offspring gets both alleles at the same time, not an average one, which is how these two concepts differ.
Additionally, the concept of epistasis could have contributed to the development of the blending model. Epistasis refers to the process of interaction between genes that affect the same trait, which results in the situation when the expression of one allele is blocked by another (Morris et al. 16-14).
In particular combinations of genes in F2 generation, when the blocked allele is not blocked anymore, the offspring can demonstrate traits that neither of the parents has. Hence, it can be mistaken for blending inheritance. However, these unblocked traits are not the average of those in parents – they are completely new.
Pleiotropy refers to one gene that affects several traits at the same time (Morris et al. 18-12). Since such kind of genes can result in some new traits in the offspring, they are somehow similar to the concept of blending. Polygenetic traits can also be mistaken for blending inheritance. While pleiotropy refers to one gene affecting several traits, polygenetic inheritance refers to one trait affected by several genes.
Although the phenotype affected by multiple genes is not an average but continuous, in some cases it still reminds the blending model. As a prime example, there is such a trait as the skin color. The darker alleles an individual has, the darker the skin color will be. However, a mother and a father with an average color of skin can still have a child with a very light skin color.
To conclude, even though the blending model was an erroneous concept, it still was based on some right ideas, which later contributed to the development of valid genetic theories.
Morris, James, Daniel Hartl, Andrew Knoll and Robert Lue. Biology: How Life Works. New York, New York: Palgrave Macmillan, 2013. Print.