Genotyp

Genotype, in biology, denotes the genetic constitution of an organism with respect to one or more genes. It encompasses the specific alleles inherited from parents and stored in the organism's DNA. In diploid species, a gene may have two alleles, which can be identical (homozygous) or different (heterozygous). The genotype, together with environmental factors, helps determine the phenotype, the observable traits; the genotype itself is typically constant from conception (except for somatic changes such as mutations in cancer). In German-language contexts, the term Genotyp is used for the same concept.

Genotype frequencies are studied in population genetics and described by models such as Hardy-Weinberg equilibrium, under assumptions of random mating and no selection. Genotyping determines the genotype at specific loci and is done by PCR-based assays, SNP arrays, targeted sequencing, or whole-genome sequencing; cytogenetic methods assess larger-scale genome structure (karyotyping).

Applications include medical genetics and pharmacogenomics, where genotype informs disease risk, prognosis, and drug response; in agriculture and breeding, genotypes guide trait selection; in research, genotyping supports studies of genotype–phenotype associations. Forensics uses STR profiling for individual identification.

Limitations include the imperfect mapping from genotype to phenotype for complex traits; environment, epigenetics, and gene interactions can modulate effects. Genotype data raise ethical and privacy concerns, requiring informed consent and secure handling.