We can observe a phenotype whether or not we understand the genetics behind it. In real life, there is a gene called HERC2 that works like I described, and most people with blue eyes have the broken allele of this gene.
Nerves, Neuroglia, and Ganglia. A nerve is a bundle of fibres (axons and/or dendrites) outside the CNS. Neuroglia are cells of the nervous system that help protect and support it. Ganglia are groups of nerve cell bodies lying outside the CNS.
A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons to peripheral organs. In the central nervous system, the analogous structures are known as tracts.Neurons are sometimes called nerve cells, though this term is potentially misleading since many neurons do not form nerves, and nerves also include non-neuronal Schwann cells that coat the axons in myelin. nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons to peripheral organs. In the central nervous system, the analogous structures are known as tracts.