A phenotype is an observable trait produced by the actions of one or more gene-encoded proteins. The phenotype is influenced by the genotype and the effects of the environment. For example, the genotype for a flower may be RR (where red is R and white is r), meaning the flower presents as being fully red as the R allele is dominant. In terms of genotype, it is the genetic composition of an organism for a particular trait (set of alleles). A gene carries a particular set of instructions for how a protein is to be made; when the gene is read, transcribed and translated into a protein, the gene is said to be expressed. The protein has specific functions depending on the gene. The protein can be categorised as either a structural protein or an enzyme. By coding for proteins, genes determine important facets of biological structure and function. The observable traits are known as the phenotype.