Polymorphism is the presence of more than two alleles for the same gene in the population.
In a diploid organism, one gene has 2 alleles but in the general population, it can have multiple alleles. A polymorphic gene is one that more than two alleles exist for it in the general population.
Examples of traits that show polymorphism are cystic fibrosis, ABO blood type, MHC's etc. Details on Blood groups and MHC's are discussed later in this section.
Polymorphisms are as a result of variations in the DNA sequence. These variants can be on a single nucleotide(known as Single Nucleotide Polymorphisms; SNP's) or a certain DNA