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.
Anatomy (Structure) of a Nerve. Nerves are the organs that make up the peripheral nervous system (PNS). They serve as information pipelines that allow the brain and spinal cord to communicate with other tissues and organs. Inside the nerves are the axon processes of sensory and motor neurons (nerve cells).