True about polymorphism is
1.Single locus ? multiple normal alleles
2.Single locus? Multiple abnormal alleles
3.Single phenotype:Single locus ? multiple normal alleles
4.Single phenotype: Single locus ? multiple abnormal alleles
Clinically harmless variation of DNA sequences that doesnot affect the phenotype.
They constitute : single base pair substitution, deletions & insertions in noncoding region.
They dont alter protein coding sequence because of degeneracy of genetic code.
So, polymorphism is single phenotype, single locus & multiple normal allele.