Allie Snell; Q2; 12/5

2: What was the most interesting thing you learned in the Making of the Fittest reading?

The most interesting thing I learned in the Making of the Fittest reading is that organisms produce both proteins that are responsibility for physiology and proteins that are responsible to the actual making of the form. The latter type, as Carroll explains, could “control the number, size, and shape of body parts, as well as the identity of cell types in the body.” These proteins are appropriately called “tool-kit proteins.” In general, these types of proteins control the where and when of gene use in a body. They may even play a part in “building or shaping” many different body parts. When these two different types of proteins are affected by mutations, the consequences are very different. Whereas a mutation in a physiological protein may alter the use or experience of the protein, a mutation in a tool-kit protein can be catastrophic in that the structure or structures it helps build are eliminated completely form the organism. Carroll gives examples of proteinx concerning the eyes. If a mutation were to occur in an opsin protein (a physiological protein), a difference in light detection may occur. However, a mutation in a tool-kit protein of the eye may result in the eye not forming at all. For these reasons, the evolution of form and structure seen in an organism usually acts through a change in the use of the tool-kit protein and not a change the actual protein.

Furthermore, gene and genome sequencing has shown that many, if not most, animals are equipped with the same types of tool-kits genes. This provides evidence for a common ancestor. However, it also begs the questions as to how wildly different forms and organisms form from the same types of genes. The answer to this question is that it is that “evolution of form” takes place through variation in genes that contain the instructions as to how tool-kit genes are used. Genes contain noncoding, regulatory DNA sequences that contain “switches” which “determine where and when each gene is used or not used.” Another crucial characteristic of these switches is that changes in one will not affect the others. This is crucial because it allows the use of one tool-kit gene to be refined without disturbing other structures.

Response to Morgan Flynn, Q2

I thought you did a really great job differentiating between the generational rate and the selection coefficient. It is interesting to think about the implications of different generational rates and different selection coefficients. Is it always beneficial to have a high generational rate? Or is there a certain rate that maximizes efficiency? How does generation rate correlate with speciation? I would also be interested in learning about how selection coefficients are used. How is a trait deemed more selective or less selective?