Genotype: the combination of allelesplugin-autotooltip__default plugin-autotooltip_bigAllele: a version of a gene. Alleles of a gene are different if they have differences in their DNA sequence. within an organism or strainplugin-autotooltip__default plugin-autotooltip_bigStrain or line: refers to a pool or colony of individuals or cultured cells of a desired genotype or phenotype that is mostly homogeneous and can be bred and/or produced in perpetuity for research or commercial purposes. “Strain” tends to be used more for microorganisms and. When used as a verb, it means to determine the genotype experimentally.