What is the difference between a phenotype and a genotype?

A phenotype is impossible to determine by looking at the organism

A phenotype is described using a pair of letters

A genotype describes the physical trait while a phenotype is a representation of the alleles present for a gene

A phenotype describes the physical trait while a genotype is a representation of the alleles present for a gene.

The genotype refers to an individual's genetic makeup, or the combination of alleles present for a particular gene, while the phenotype is the physical expression of those alleles. In other words, the genotype is the underlying genetic code while the phenotype is the observable characteristics or traits that result from that code. For example, a person with a genotype for blue eyes will have that allele present in their DNA, but whether or not they actually have blue eyes (the phenotype) will depend on other factors such as their environment and interactions with other genes.