Noun. 1. axon-long nerve fiber that conducts away from the cell body of the neuron. axone. nerve fiber, nerve fibre-a threadlike extension of a nerve cell.nerve cell, neuron-a cell that is specialized to conduct nerve impulses. nerve end, nerve ending-the terminal structure of an axon that does not end at a synapse.oun. 1. axon-long nerve fiber that conducts away from the cell body of the neuron. axone. nerve fiber, nerve fibre-a threadlike extension of a nerve cell.
The genetic code is a nearly universal language that encodes directions for cells. The language uses DNA nucleotides, arranged in codons of three, to store the blueprints for amino acid chains.
It is passed down directly from mother to child, and it accumulates changes much more slowly than other types of DNA. Because of its unique characteristics, mtDNA has provided important clues about evolutionary history. For example, differences in mtDNA are examined to estimate how closely related one species is to another.