genotype

The genes carried by an individual member of an organism. The term may refer to the total complement of genes or to particular genes at specified loci in the chromosomes. The interaction of gene products (RNA, protein) with each other and with the environment in which the organism develops gives rise to the phenotype - the characteristics that are observed.

Typically, one refers to an individual's genotype with regard to a particular gene of interest and, in polyploid individuals, it refers to what combination of alleles the individual carries (see homozygous, heterozygous). Any given gene will usually cause an observable change in an organism, known as the phenotype. The terms genotype and phenotype are distinct for at least two reasons:

To distinguish the source of an observer's knowledge (one can know about genotype by observing DNA; Genotype and phenotype are not always directly correlated. Some genes only express a given phenotype in certain environmental conditions. Conversely, some phenotypes could be the result of multiple genotypes. The genotype is commonly mixed up with the Phenotype which refers to the physical appearance

The distinction between genotype and phenotype is commonly experienced when studying family patterns for certain hereditary diseases or conditions, for example, hemophilia. Sometimes people who do not have hemophilia can have children with the disease, because the parents each "carried" hemophilia genes in their body, even though these genes have no effect on the parents health. Healthy people who are not carriers and healthy people who are carriers of the hemophilia gene have the same outer appearance (ie they do not have the disease), therefore they are said to have the same phenotype. However, the carriers have the gene and the other healthy people do not (they have different genotypes).

With careful experimental design, one can use statistical methods to correlate differences in the genotypes of populations with differences in their observed phenotype.

Inspired by the biological concept and usefulness of genotypes, computer science employs simulated genotypes in genetic programming and evolutionary algorithms.