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.
hold one's nerve/keep ones's nerves meaning, hold one's n... | English Cobuild dictionary. nerve. 1 n-count Nerves are long thin fibres that transmit messages between your brain and other parts of your body. ...spinal nerves., ...in cases where the nerve fibres are severed. 2 n-plural If you refer to someone's nerves, you mean their ability to cope with problems such as stress, worry, and danger.