Genotype

A genotype is the specific genetic constitution or makeup (genome) of an individual in terms of its DNA. The DNA through the genotype determines the hereditary potentials and also the limitations of an individual person (or indeed that of any organism) from its embryonic formation through to adulthood. For organisms that reproduce sexually, the inherited genotype contains the entire complex set of genes from both parents. This means that after sexual reproduction, it is certain that each individual will have a unique genotype, except for identical twins, triplets, and so forth, who are derived from the same fertilized egg. This contrasts with the phenotype of an individual which involves the physical appearance and constitution of an organism.

For medical research, the genotype is crucial in working out ways of treating diseases in general, separated from the person suffering from the disorder. This has been particularly important in the treatment of cancer, with oncologists and their research teams anxious to work on the fundamental causes of cancer and try to eliminate hereditary factors that might otherwise influence their work. Much of the original research and the development of ideas on genotypes was carried out by the Danish botanist and geneticist Wilhelm Ludvig [Page 730]Johannsen. He conducted many experiments in plant heredity and these tended to support the mutation theory of the Dutch botanist Hugo de Vries, which argues in favor of gradual change through heredity rather than Charles Darwin's concept of natural selection. Johannsen coined the term genotype, based on genus, and also the term phenotype.

Although research in genotypes has aided much medical research, one of the emerging problems with the increased popularity of genotype research has occasionally led to some people, who have no real understanding of medicine, to become fatalistic and feel that particular disorders from which they suffer are part of their inherited genotype and ignoring environmental and other factors.