Differences between Mendelian and Non-Mendelian Inheritance - Essay Example

Non-Mendelian inheritance on the other hand refers to the pattern of inheritance in which the traits do not separate and are not in agreement or accordance with Mendel’s laws.

In Mendelian inheritance, a trait is contributed by each parent in one out of two possible alleles.

It would not then be wrong to term monogenic traits as Mendelian inheritance as they obey Mendel’s laws, while the polygenic inheritance traits can be termed as Non-mendelian inheritance. Thus, the Non-mendelian inheritance could also be referred to as the inheritance of a phenotypic characteristic that can be ascribed to more than two genes. This implies that monogenic traits are examples of Mendelian inheritance as they follow the principle of separation of traits as present in Mendelian inheritance. Polygenic traits on the other hand are examples of Non-mendelian traits as they do not follow the patterns of the separated traits that are synonymous with Mendelian inheritance (Berg & Maxine, 1992).

            Mendelian inheritance could also be termed as traits that are controlled by a single locus and the implication of this is that, they illustrate a plain Mendelian inheritance pattern inheritance (Berg & Maxine, 1992). Non-mendelian inheritance on the other hand is controlled by several loci and the implication of this is that their pattern is more complex than those of the Mendelian inheritance. The skin color of humans is a very good example of a polygenic trait and this also makes it a good example of Non-mendelian inheritance (Berg & Maxine, 1992). Several genes contribute to the determination of the natural skin color of an individual and this is the reason that the human skin color is a good example of Non-mendelian inheritance. Diseases that arise from Mendelian inheritance are usually due to a mutation in the single gene that is present in them. These diseases are inherited according to Mendel’s law and examples of such diseases are cystic fibrosis, Tay-Sachs disease, sickle-cell anemia, and xeroderma pigmentosa. It should be noted that these diseases are the ones that are controlled by a single gene and are limited only to the Mendelian inheritance. Diseases that are controlled by multiple genes are Non-mendelian inheritance and these diseases are diabetes, autism, cancer, cleft palate, diabetes, leukemia, pyloric stenosis, schizophrenia, etc.

            Mendelian inheritance patterns involve genetic materials that influence the outcome of the characteristics or traits of the organism directly, while Non-mendelian inheritance involves genes that do not influence the outcome of the characteristics or traits of the organism directly. The implication of this is that the Mendelian inheritance obeys Mendel’s laws, while the Non-mendelian inheritances do not obey Mendel’s laws. It should be noted that, while most of the genes in the eukaryotic species follow the Mendelian pattern of inheritance, some of them do not.

            It also becomes pertinent to analyze the polygenic nature of schizophrenia vis-a-vis the liability threshold models. It is also important to elaborate on how these are related to certain genes and the extent to which they can be held at stable frequencies despite their harmful effects. Schizophrenia has a polygenic nature as it has an intermittent binary distribution and the implication of this is that they are either present in the gene of an individual or not (Jablensky, 1995). The threshold effect or models of schizophrenia is what contributes to its polygenic nature and makes it look discontinued and this is the reason that certain genes can be held at stable frequencies despite their harmful effects (Jablensky, 1995). Thus, schizophrenia could be inherited multifactorial and it works based on the threshold models it is on this note that, they could be called Multifactorial inheritance with a threshold. It should be noted that, despite the polygenic nature of schizophrenia, there has not been any characteristic genetic indicator that has been certainly determined. It is due to genetic makeup and the polygenic nature of schizophrenia that certain people show different symptoms when they have the illness. The multifactorial threshold model shows that the quantitative trait that is associated with the disease is dependent on several factors and they follow a gamma distribution. The implication of this is that certain genes can be stabilized to a particular frequency without causing significant problems despite the harmful effect it could have on an individual.