It is currently thought that only about 2% of the human genome codes for functional proteins, yet more than 80% of transcripts encoded in the genome may have some biochemical activity. In a recent study, Djebali et al. (2012) used ultra-deep sequencing of RNAs from different cell lines and concluded that ∼75% of the genome is transcribed at some point during the cellular life cycle. These extensive studies using sequencing and sophisticated ncRNA prediction algorithms have led to the identification of thousands of ncRNAs in the human genome, and perhaps many more remain to be discovered (Majer and Booth, 2010; Yang et al., 2010).
