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Gene duplication and crotamine

Submitted by kheredia on Thu, 10/31/2019 - 10:53

Gene duplication, regulatory mutations, and the coding sequence all play different but important roles in the evolution of venom. Gene duplication, which is a mechanism where genetic material is generated/duplicated, and this area of DNA contains a gene. This event allows one copy to continue with the original function of said gene, while the other copy has the ability to evolve into something else. A regulatory mutation affects the temporal or spatial regulation without causing a complete loss of the gene product. This basically means that the mutation can change the different tissues the gene is expressed in, without losing the purpose/function of the gene itself. A coding sequence mutation is when a base is changed within the amino acid, and this can cause either a nonsense or a missense mutation (can change the whole amino acid or just the base).

Gene duplication plays a role in the evolution of crotamine because after the defensins evolved from a common ancestor and was inherited between many animals, including snakes, the extra copies of this gene created by gene duplication allowed the defensins to become more specialized. In the case of these snakes, the specialization was for attacking different pathogens found in the pancreas. This duplication, according to Fry, began to change the actual shape of the protein (after many duplications). A new shape meant a new function, which leads us from defensins to crotamine. The regulatory mutation changed the location of where the protein was being produced (from the pancreas, to the mouth). This mutation played a huge role in the usage of this gene. With a gene that damaged muscles instead of pathogens, found in a place crucial for killing prey it could easily used to incapacitate and kill the desired prey. As for the coding sequence mutation, a simple change of one amino acid could cause a cascade of other elements that led to crotamine as a deadly, venomous, protein. This type of mutation could explain how ancient venom is, especially in certain snakes that are deemed non poisonous. Meaning that a coding sequence mutation could’ve caused earlier ancestors to produce crotamine. This, along with gene duplication and regulatory mutation, played big roles in the evolution of crotamine, from defensins.