Monday, August 29, 2016

Genetic Evolutionary Advancement Discovered in the Saliva of Primates

In a recent study conducted by Greece and the United States, the salivary mucin-7 gene (MUC7) was questioned and observed. This gene dictates to the body its instructions on how to generate a salivary protein with the same name. This protein makes up a molecule that is shaped like a bottlebrush which is what gives saliva its sticky and slimy consistency. Within this gene are the set of instructions for creating the imperative parts of the bottlebrush. These genes were repeated many times in each of the species of primates that were examined. For example, humans had 5-6 copies, gorillas had the fewest copies with only 4-5 copies and the African green monkeys had the most copies with 11-12 copies. It was concluded by researchers that having more than one copy of these repetitious instructions most likely granted an evolutionary advantage to primates. Perhaps this occurred by intensifying the important traits that saliva possesses such as the capability of binding microbes (which would aid in avoiding disease) as well as its lubricity.
Genomic location, organization and subexonic copy number variation of the MUC7 gene in the human reference genome: the gray bar indicates the chromosomal band where MUC7 resides; the zoomed-in version of the gene shows the two coding exons (thick blue bars), the UTR region at the 3’ and 5’ ends (thin blue bars) and intronic regions (blue line in-between exons). Start and end of the transcript are indicated by the numbers at each end. The different functional domains within the MUC7 protein are designated by different colors at the bottom of the panel. Image credit: D. Xu et al.
In the MUC7 gene, the replicated important instructions occurring over and over resulted in denser, longer proteins which are very skilled at grabbing onto the dangerous microbes and lubricating the throat and mouth. The repetition of the MUC7 gene is titled tandem repeats which are short threads of DNA found many times within the gene. This helps to portray that as primates went through evolution, the genetic material within their tandem repeats occasionally changed in some areas. However, this genetic material stayed the same in one very important way: the pieces of the DNA that dictated to the body the instructions on how to create amino acids remained in all primates. The findings suggest that tandem repeats may act as modular building blocks for expeditious evolutionary changes. 
A baby salivatesThis is very interesting because it suggests that as humans (a member of the primate species) have evolved, so too has our saliva which may be helping to protect against diseases and also aid in digestion by properly lubricating the mouth. In comparison to other species, we have many more copies of MUC7 which is believed to help us speed up the process of getting rid of the disease causing pathogens within the oral cavity. The fact that there are tandem repeats within the MUC7 gene eludes to the possibility that many other genes within primates may also adapt quickly to the environment and go through evolutionary changes as well.

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