In humans sequence

If in a DNA or protein sequence a single position is variant, this may be called a polymorphism or mutation. The difference is set by convention a mutation is rare, and a polymorphism is common. By implication, a mutation may be deleterious, or in rare cases it may be advantageous for the reproductive fitness of its carriers. A widespread polymorphism, on the other hand, is unlikely to affect the fitness to such an extent. A frequency value of 1 % of the polymorphic allele is usually taken as a threshold between mutation and polymorphism (Ki-mura, 1983 Li, 1997). A polymorphic site is called biallelic if two variants segregate in the population, and multiallelic if there are more than two variants, which is a rare event in human sequences. 

Liu H, Han H, Li J, Wong L (2003) An in-silico method for prediction of polyadenylation signals in human sequences. Genome Inform 14 84-93... 

Akhtar MN, Bukhari SA, Fazal Z, Qamar R, Shahmuradov I (2010) POLYAR, a new computer program for prediction of poly(A) sites in human sequences. BMC Genomics 11(1) 646... 

---