Final answer:
SNPs are common genetic variations, often used as markers for disease susceptibility, but they are not always associated with diseases.
Step-by-step explanation:
All of the following are true of single nucleotide polymorphisms (SNPs) EXCEPT that SNPs are always associated with disease traits. SNPs are indeed the most common type of genetic variation in humans, and they can be used as genetic markers for disease susceptibility. They involve the substitution of one nucleotide for another in the DNA sequence. However, it is not true that SNPs are always associated with disease traits; many SNPs have no effect on health at all and are simply harmless variations in the genome.