Genotype
The genotype is the genetic constitution of an organism, mainly its genome.[1] The term is contrasted with the term phenotype, as follows:
- genotype + environment → phenotype
The terms were invented by Wilhelm Johanssen to distinguish between inherited and environmentally produced variation.[2] "The distinction was not new. It had, for instance, been discussed by Francis Galton as nature vs. nurture.[3]
The extent to which the genotype influences the phenotype varies hugely. Some aspects of the phenotype are almost entirely determined by heredity, such as eye colour and blood types. Human language is an interesting case. The capacity to learn and speak a language is entirely inherited, but which language is spoken is entirely learnt, and hence is environmental.
Genotype Media
Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of petal colour in a pea plant. The letters B and b represent alleles for colour and the pictures show the resultant flowers. The diagram shows the cross between two heterozygous parents where B represents the dominant allele (purple) and b represents the recessive allele (white).
An example of a pedigree for an autosomal dominant condition
An example of a pedigree for an autosomal recessive condition
