The vast majority of human DNA lies outside of the genes within the cells. Of this, recent work has discovered that 85% of these stretches of DNA appear to make RNA - which, for the most part, has yet-to-be-determined functions.
“Today, scientists estimate that only 1.5 percent of the genome consists of genes.”
The lab investigates the remaining 98.5% - which (referencing similarly-scaled problems in cosmology) they call the 'Dark Matter' of the human genome.
“Much of the human genome is composed of intergenic sequence, the regions between genes. Intergenic sequence was once thought to be transcriptionally silent 'junk DNA', but it has recently become apparent that intergenic regions can be transcribed. However, the scope, nature, and identity of this intergenic transcription remain unknown. Here, by analyzing a large set of RNA-seq data, we found that >85% of the genome is transcribed, allowing us to generate a comprehensive catalog of an important class of intergenic transcripts: long intergenic noncoding RNAs (lincRNAs). We found that the genome encodes far more lincRNAs than previously known.”
“We believe that the regulatory noncoding RNAs that have been discovered are just the 'tip of the iceberg' in a set of important biology that we are far from understanding.”
Further reading : Junk DNA: A Journey through the Dark Matter of the Genome by Professor Nessa Carey, Columbia University Press, 2015.
“Junk DNA can play vital and unanticipated roles in the control of gene expression, from fine-tuning individual genes to switching off entire chromosomes. These functions have forced scientists to revisit the very meaning of the word “gene” and have engendered a spirited scientific battle over whether or not this genomic “nonsense” is the source of human biological complexity.”