Qualitative Traits In Eukaryotes
One example of complex traits is quantitative traits. These traits are also known as polygenic traits since its phenotype is not coded by one gene alone but by many (through their cumulative action). So, a quantitative trait can be summarized as a measurable phenotype dependent on the action of more than one gene and other non-genetic factors like environmental conditions. These traits are subsequent distributions of varying phenotypes that vary widely among individuals. Probably the main reason quantitative traits are considered complex is because they can’t be analyzed as Mendelian traits. So, quantitative traits won 't yield precise results as Mendel 'simpler traits because a quantitative trait will not be influenced by one gene alone. So, the fact that more than one gene govern quantitative traits (traits that can be expressed through epistasis) makes it hard to analyze quantitative traits through simple methods. Also, it is vital to mention that quantitative traits are not only influenced by genetics alone but also by the environment. So, quantitative traits don’t oppose Mendelian traits; these traits just happen to pose a harder analytical …show more content…
In fact, there is a wide range of environmental cues that account for differences in gene expression. For example, let us consider the example that Zimmer and Emlen provided in Chapter 5. Here, the example analyzed was the height patterns observed in Guatemalan people living in the US compared to their counterparts in Guatemala. The ones living in the States were taller than their poorer, not-so-well fed counterparts. This evidence helps to understand the role that the quality of the diet plays in gene expression. Stress levels can also change the nucleosome and cause changes to gene expression. Other factors such as exposure to chemicals, radiation, and other factors can play a significant role in gene expression as well.
If we want to analyze phenotypic plasticity, it is necessary to point out what we understand by it. So this term refers to the changes that a single genotype carries out in a phenotype in response to different environments. Therefore, reaction norms serve to clarify how phenotypic plasticity takes place since reactions norms describe it. In other words, it shows how environments and genes shape phenotypic plasticity. But, above all, it allows us to access the role of the environment as a primary