Practice question

Micro RNAs are approximately 22 nucleotide regulatory RNAs derived from hairpin precursors and lack poly-adenine tails. Whole transcriptome and messenger RNA sequencing protocols often include size selection steps that discard RNAs below 200 nucleotides or enrich poly-adenylated species, causing loss of micro RNAs. Small RNA sequencing employs specialized library preparation, preserving 18-35 nucleotide species, ligating adapters directly to 3 prime and 5 prime ends of total small RNA, reverse transcribing without fragmentation, and sequencing. This approach allows precise identification, quantification, discovery of novel micro RNAs and analysis of isoforms and modifications.