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Snake Poison

Submitted by rmmcdonald on Fri, 11/22/2019 - 10:16

Gene Duplication: a spontaneous event such as a mutation or other factors may result in DNA polymerase or other mechanisms mistakenly duplicating a gene. Further mutations in the regulatory or coding region of one of the duplicated genes alters when, what, and how much of that gene may be expressed. These two copies of the same gene (found within a species) are called paralogs.

Regulatory mutation: mutations in the regulatory region of a gene will alter when and how much of a gene will be expressed. The genetic code of the gene itself will not be altered, preserving the phenotypic expression of the gene. However depending on the level of expression caused by a mutation in the regulatory sequence the phenotypic expression of the gene may also be altered.

Coding sequence mutation: Since the regulatory sequence remains the same, gene will be expressed at the same time, place, and level. However depending on the type of mutation in the gene it may be a nonsynonymous or synonymous. A nonsynonymous mutation may result in a loss of original function of the gene, but gain function in another pathway. If the protein is promiscuous it might not completely lose its original function, just alter one of its many active sites. 


Crotamine likely evolved from beta defensin genes through a combination of gene duplication, regulatory mutation, and coding sequence mutation. Gene duplication must have occurred first because the initial gene, beta defensin, is a gene critical to an organism's function therefore that gene must be conserved. When an ancestor had two copies of the beta defensin gene, one of the copies then had a spontaneous mutation in the regulatory sequence, expressing beta defensin in the fangs at higher concentration. This evolutionary step might have happened before, after, or at the same time as a series of mutations in the coding sequence of the copied beta defensin gene in order to code for a poisonous protein instead.