∞ generated and posted on 2016.08.21 ∞
An organism's hereditary information.
Genotype in modern, cellular organisms is encoded by the molecule, DNA. In certain viruses, though, it consists instead of RNA. Literally, genotype is the sequence of nucleic acid bases (nucleotides) making up the genome of an organism.
Genotype, more abstractly, is a description of what alleles are carried by an organism, where different members of the same population will carry different alleles at the same locus. More concretely, genotypes can interact with as well as modify environments by giving rise to phenotype, where phenotype is accomplished via the expression of genotype, particularly of genes. The purpose of phenotype, ultimately, is the generation, in part via genotype replication, of new organisms.
The concept of genotype preceded by decades the concept of the hereditary material of cells and organisms. The idea of what genotype is, in fact, closely follows the idea of what a gene and therefore what a locus is.
Originally, genes were just heritable units that somehow were associated with specific phenotypic traits. Later, genes came to be seen as entities that gave rise to enzymes, then more generally proteins, and then more specifically to polypeptides.
Not so long after it became well established that polypeptides were linear molecules, then so too was the double helical structure of DNA established. What followed that discovery was the idea of a correspondence between the linearly encoded genotype and how this code could give rise to the three-dimensionality not just of proteins but of phenotype in general. For additional discussion, see what is a gene.