What is the difference between multiple alleles and polygenes

Mendel was the first known person to have explained the fundamental aspects of genetics. After his death, many scientists carried out experiments to reconfirm the findings of Mendel. Extended researches later proved that some traits function in different ways.

Multiple alleles and polygenic traits are two such exceptional cases that cannot be explained by the theories of Mendel. The difference between multiple alleles and polygenic traits will be discussed in this article, in detail. Certain characteristics of an individual are resulted by two or more alleles. This condition is known as multiple alleles. One of the key characteristic features of multiple alleles is that all the alleles that are responsible for a characteristic of an individual lie on the same locus in the homologous chromosome.

All alleles represents the same character, but with slightly different degrees. In this condition, the wild type is always dominant over the mutant form. However, intermediate or incomplete dominance may also be present. These pieces of the proteins formed in multiple places can be combined in almost infinite combinations. This makes it possible for the immune system to respond to threats that may not have existed in a previous genetic generation.

In a similar manner enzyme proteins can be made from non continuous parts of the DNA. Being polygenic organisms can product enzymes to meet new challenges. A surprising example is the development of enzymes in some bacteria that can digest plastics. Polygenic inheritance makes for almost infinite possibilities. What is the difference between multiple alleles and polygenic inheritance?

David Drayer. Jan 25, The difference is the number of strands of DNA involved. Multiple alleles are the alternative forms of a gene when a particular gene comprises more than two alleles. Typically, every gene comprises two alternative forms: the dominant allele and the recessive allele. However, some genes comprise more than two alleles. Multiple alleles are situated at the same locus of homologous chromosomes. Homologous crossing over does not occur between homologous chromosomes containing alleles of the same gene.

The influence of multiple alleles is on a single trait. Comprising of multiple alleles for a particular gene is a type of non-Mendelian inheritance pattern. Multiple alleles may produce either codominance or incomplete dominance patterns. Thus, a mixture of phenotypes can be visible in the offspring. A mixed type of dominant phenotypes can be observed in codominance while a blend of phenotypes can be observed in incomplete dominance.

Figure 1: Inheritance of ABO blood types. The human blood type is determined by multiple alleles. Three allele types are involved in determining the blood type; I A , I B , and i. The type O blood is determined by the combination of two recessive alleles, ii. The inheritance of ABO blood types in humans is shown in figure 1.

A trait that is controlled by more than one gene is referred to as a polygenic trait. Each gene is located in different loci of different chromosomes. Polygenic traits are a type of non-Mendelian inheritance. The polygenic traits show a continuous variation of the character. Thus, polygenes show incomplete dominance. The distribution curve of the polygenic inheritance is bell-shaped. Polygenes show a great significance in evolution since they produce many different genotypes.