A SNP is a variation of a single nucleotide between individuals. These polymorphisms can therefore be used to discern small differences both within a population and among different populations.
President of the United States. The President of the United States is the head of state of the U.S., the chief executive of the federal government, and Commander-in-Chief of the armed forces. The United States was the first nation to create the office of President as the head of state in a modern republic.
The President of the USA is the Commander in Chief of the American Armed Forces. By deliberate design, that position can only be held by a civilian. It reinforces the concept that the military is subordinate to the rule of law as created by civilians in the form of the elected government.