SNP waxay u taagan tahay "Single Nucleotide Polymorphism." Dhinaca hidde-sideyaasha, SNP waa kala duwanaansho hal boos oo isku xigta DNA ah oo ka dhex jira shakhsiyaadka noocyada. Waxay dhacdaa marka hal nucleotide (A, T, C, ama G) oo ku yaal meel gaar ah oo genome ah ay ka duwan tahay shakhsiyaadka. SNPs waa nooca ugu badan ee kala duwanaanshaha hidde-sidaha ee bini'aadamka waxaana loo isticmaali karaa in lagu raad raaco u nuglaanshaha cudurka, loo aqoonsado abtirsiinyada, iyo fahamka kala duwanaanshaha hidde-sidaha ee gudaha iyo ka dhexeeya dadka.