Final answer:
The percentage of unique non-repetitive sequences in non-coding DNA varies between species, with up to 98% of eukaryotic genomes like humans being non-coding, but only a fraction of this constituting unique non-repetitive sequences. This area is under active research, and our understanding of the functional genome is evolving, making it difficult to provide an exact percentage.
Step-by-step explanation:
The question asks about the percentage of non-coding DNA that is unique non-repetitive sequences such as viral sequences, pseudogenes, or non-coding RNA. In prokaryotes, the genome consists mostly of coding DNA with only about 12% being noncoding sequences. Conversely, in eukaryotes, such as humans, noncoding DNA can constitute up to 98% of the genome. However, only a small portion of this non-coding DNA is composed of unique non-repetitive sequences. These sequences include functional elements such as promoters, enhancers, silencers, insulators and genes for non-coding RNAs that are involved in transcription regulation and other cellular processes. The exact percentage of unique non-repetitive sequences in noncoding DNA varies between species and with continuous research, previously thought non-informative or 'junk' DNA is showing functionality, reducing the percentage considered non-informative.
For a eukaryotic genome like humans, this percentage is continually being revised as new research discovers functions for previously misunderstood DNA regions. With the discovery of functions for miRNA genes and the debate over the existence of 'junk DNA', it's evident that our understanding of the functional genome is evolving. Hence, it is challenging to give an exact percentage for unique non-repetitive non-coding sequences because this area of genomics is under active research and the numbers are subject to change with new discoveries.