Throughout the first chapter of the book, Shenks opposes the idea that traits are as clearly defined as the genetic model that Mendel created. He argues that all traits can not be evaluated with a simple punnett square. While Shenks does admit that many physical traits such as hair color and eye color are "near Mendelian", he also notes that this does not mean a "gene-environment interaction" did not occur (24). Even in these clear-cut examples of inheritance, the environment is still interacting and affecting the genes. Shenks also says that as traits grow in complexity, they act less and less Mendelian.
What causes the variation in trait predictability? Is Mendel's approach to genetics incorrect? Do you foresee a day that more complex traits can be predicted? In your response, comment on the types of traits that Mendel first observed (Campbell 262-269). Also, comment on the number of genes/proteins involved in simple traits such as hair color versus the number of genes/proteins involved in complex traits such as personality.
Jonah May (Jonah2020@aol.com)
The environment we live in, especially today's modern society, is extremely fast moving, dynamic, and complex. Therefore, when it interacts with our genes it creates an effect impossible to predict completely. Mendel wasn't right, but he also wasn't wrong. He created the building blocks for genetic understanding, which is basically as far as we can go in predicting genetics, because of the complicated GxE interaction. I do not ever see a day that we could predict traits because of the complexity of the interaction. The argument could be made that technology could catch up eventually somehow; however, as technology for genetics increases, other technology will also advance, complicating society and therefore the environment and its relationship with our genes even further. As shenk wrote, genes "are active participants in the developmental process and are built for flexibility" (24). Genes aren't meant to be predictable. If they were predictable, this world would be much more plain and boring.
ReplyDeleteMendel observed flower color, flower position, seed color, seed shape, pod shape, pod color, and stem length. The genes he tested explain why he proposed the model that he did. All the seed and pod genes are genes which are expressed very soon after reproduction in a young plant's life. This means that there wouldn't have been much environment to affect the genes yet, so Mendel's results for them were very close to correct. The flower color trait is a very simple one, which probably also doesn't experience much environmental interaction. However, the flower position and stem length would have a huge impact from the environment based on sunlight, wind, and many other factors. On these traits, chance most likely caused him to get results which supported his punnett squares.
While Personality is much more complex than hair color, even hair color which has multiple genes (http://www.huffingtonpost.com/2012/03/20/neanderthal-eyes-brown-dna-study-genome_n_1367426.html) involved is still very complex. For example, in a study done on mice, it was found that the diet of mice could change the hair color of the offspring when it lacked a certain key ingredient (http://www.philly.com/philly/health/HealthDay662828_20120316_Genes_May_Hold_the_Key_to_Aging_Skin.html?cmpid=138896554). This shows that even in what seems like it would be a simple trait, there is great complexity. The environment of the parents played a role in determining the gene expression of the mice offspring. Genetics have an inconceivable amount of interactions and complications, which humans most likely will never be able to predict like Mendel thought he could.
Josh Weisberg (superswimmer51@sbcglobal.net)