A Single Nucleotide Polymorphism (SNP) is a variation in a single nucleotide, which is the basic building block of DNA. In a SNP, one nucleotide in the DNA sequence is replaced by another, such as changing an adenine (A) to a guanine (G). These variations can occur in coding regions of genes or in non-coding regions, and they can influence how genes function. SNPs are important in genetics because they can affect individual traits, disease susceptibility, and responses to drugs. Researchers study SNPs to understand genetic diversity within populations and to identify genetic markers associated with conditions like diabetes or cancer.