Last week in class we had some discussion about which type of mutation would be the most important to evolution. We were debating about whether mutation in the regulatory, the cis mutation, or mutation in the gene, the trans mutation, would give rise to new traits.
The cis compartment of a gene is an DNA untranslated region located in the 5' position (upstream) to that gene. The cis regulatory region is very important in turning a gene on/off or the level of expression. A lot of different traits in the animal kingdom are the result of different regulation of the same gene. Take the arm as an example, most vertebrate has very similar arm structure: one bone, two bones, a bunch of little bones and digits. The genes for these bones are similar, but different level of expression caused them to have different size and thus a different shape. Mutation in the regulatory sequence can cause changes in the organism's final form without causing a different protein structure.
The gene is the DNA sequence that actually codes for the proteins. Mutation in the gene gives rise to new proteins. Evolutionary, new proteins are very important in the appearance of new traits. RuBisCO, for example, is a protein originate from changes in the protein structure. This protein allows organism to fix CO2 and do photosynthesis producing O2. This is a very important historical event because the oxygen produced could be used in cellular respiration producing a lot of energy. And multicellular organisms require a lot of energy to maintain their system.
RuBisCO 3D ribbon structure
There were many argument for both sides, cis and trans. For the important of trans mutation, one can say that without the actually gene codes for the protein, there would be no traits. The counter argument would be that without the regulation sequence, the promotor, the gene would not be expressed. In addition a lot of morphological traits are actually derived from the changes in expression of the same genes, not the changes in the genes themselves. On the contrary, the binding protein in the regulatory elements are actually the product of the trans elements.
Cis and trans do not work without the other. A gene without a promoter is not expressed. A promoter without a gene would cause expression of a nonsense protein. It seems like they are equally important. Rather asking which one influenced evolution greater, we should spend our time studying and expanding the knowledge of how cis and trans interact.