What are alleles, genetic variant, genotype, locus, and SNP?

  • Alleles: variant forms that a locus may present
  • Genetic variant: locus with more than one allele in a population
  • Genotype: the combination of two alleles inherited at a specific locus. The genotype is homozygous if the alleles are the same; otherwise, heterozygous.
  • Locus (plural loci): a specific location in a DNA sequence and may be used to refer to a SNP or a region of DNA sequence
  • Single nucleotide polymorphism (SNP): a type of genetic variant where the genetic code varies by a single base pair. Polymorphism means the allele frequency should be over 1% in the population.