Polymorfismi

Polymorfismi, in genetics, are DNA sequence variations that are common in populations. A polymorphism is typically defined as a variant that appears in at least about 1% of individuals, distinguishing it from rare mutations. The term covers several classes of genetic variation, including single nucleotide polymorphisms (SNPs), insertions and deletions (indels), copy number variations (CNVs), inversions, and microsatellites or simple sequence repeats.

Many polymorphisms have no measurable effect on phenotype, but others influence traits such as metabolism, disease susceptibility, or drug response. SNPs account for the largest share of polymorphisms; while some variants in coding regions may alter amino acids, the majority are noncoding and can affect gene regulation or splicing.

Variant frequencies differ among populations due to evolutionary forces such as natural selection, genetic drift, migration, and demographic history. Population genetics concepts, including allele frequency and Hardy-Weinberg equilibrium, underpin studies of polymorphisms.

Polymorfismi are central to modern genetics. They enable genome-wide association studies (GWAS) that link variants with diseases, underpin pharmacogenomics to tailor therapies, and assist forensics through short tandem repeats. Common examples include HLA gene polymorphisms and the ABO blood group system.

Detection and study of polymorphisms rely on sequencing, genotyping arrays, and targeted assays. Public databases, such as large genome projects, catalog polymorphisms across populations and support research and clinical translation.