As I mentioned last week, this post will shed some light onto the concept of pleiotropy. Pleiotropy was seen to play a role in the psychiatric disorders discussed last week, but it was never clearly stated exactly what this means. I've found some information on the history of pleiotropy and how its definition has evolved in science over the past few years and will probably continue to evolve as more information is discovered.
Pleiotropy is when a locus on a gene has control over multiple phenotypes expressed by that organism (Stearns, 2010). Stearns (2010) describes pleiotropy as a type of mutation that can be observed as different phenotypes arise from a change in one gene. This phenomena is hard to distinguish from phenotypes linked by similar genes, but pleiotropy is still believed to greatly influence, "aging, selection, adaptation, speciation, and human disease" (Stearns, 2010). We saw one example of its role in psychiatric disorders last week. The idea of pleitotropy dates all the way back to Gregor Mendel's first workings with genetics (Stearns, 2010). He observed the linked inheritance of seed coat color, flower color, and axial spots on a plant and believed that these traits must have been expressed by the same gene (Stearns, 2010). Mendel didn't specifically come up with pleiotropy, but he did introduce some of the first thoughts on the matter. Ludwig Plate studied genetics further and is the person who gave the idea of pleiotropy its name (Stearns, 2010). He explained how a pleiotropic gene would express multiple traits and that because these traits were all associated with one gene, they would always be correlated with one another (Stearns, 2010). Later research led to the discovery that a locus could have multiple reading frames that translated to different proteins (Stearns, 2010). This occurs through alternative stop/ start codons and alternative splicing within the locus (Stearns, 2010). Differences in the start and stop codons in the locus cause varied forms of proteins which, in turn, lead to different functions and multiple phenotypes (Stearns, 2010). On the other hand, alternative splicing cuts out different exons which lead to varying proteins (Stearns, 2010). If the different combinations of exons from the same locus are spliced then this results in multiple proteins which is seen as pleiotropy (Stearns, 2010). It is believed that many genes exhibit pleiotropic effects in that they correspond to multiple proteins, but of this large quantity, only a few genes actually express differences in multiple phenotypic traits (Stearns, 2010). Pleiotropy can lead to both increased and hindered adaptation of populations in an evolving environment depending on the circumstances (Stearns, 2010). In some cases it may allow species to develop newly adapted traits with ease, while at other times the multiple functions associated with a specific gene will prevent evolution from targeting the specific function that needs to adapt (Stearns, 2010). Scientists are still studying pleiotropy and its roles in evolution.
Good job on making this concept clear and easy to understand! It’s amazing to think that one gene can potentially have numerous effects on an organism. I am intrigued about how pleiotropic genes are regulated. Are they regulated in a similar manner to other genes? I was also curious if pleiotropic genes are more common in species occurring in unpredictable environments? A thought-provoking post.
ReplyDeleteI think pleiotropic genes are regulated in a similar manner to other genes. These genes act normally but are able to encode for different proteins. In this article, pleiotropic genes are thought of as mutations, so their regulation may be similar to other genes but the off-chance of a difference in splicing or encoding of start and stop codons may be the cause for such distinct changes in phenotypic expression. I'm not entirely positive if pleiotropic genes are more commonly found in unpredictable environments but I think that would make the most sense. These genes play a major role in evolution and in increasing an organism's fitness. In dynamic environments the need to adapt is essential to survival. As a result, new phenotypes arise and these may be the product of pleiotropic genes.
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