Non-coding DNA is DNA that does not encode a protein sequence. It includes many regulatory regions, introns, noncoding RNA genes and repeated sequences. Some regions have well-established functions, while others have uncertain or dispensable contributions under tested conditions. The category therefore specifies coding status rather than a single functional verdict. Conversely, finding biochemical activity at a noncoding region does not by itself establish that the activity is required for organismal fitness. [ref]
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