**3.2. Classification of lncRNAs**

The biotypes of lncRNAs were identified with respect to their genomic localization, and were mainly categorized into intergenic, intronic, sense, antisense, and bidirectional lncRNAs. As the term suggest, the intergenic lncRNA are transcribed from the region amid two genes, while introns are the source of intronic lncRNA [45]. The sense and antisense lncRNAs are derived from overlapping region of exons on the sense and antisense strands, respectively [18], when the transcription of lncRNA is initiated in the juxtaposition of adjacent mRNA on complementary strand, termed as bidirectional lncRNA [45].
