Duplex-specific nuclease (DSN) is an enzyme purified from hepatopancreas of Red King (Kamchatka) crab (Shagin et al., 2002). DSN shows a strong preference for cleaving double-stranded (ds) DNA and DNA in DNA-RNA hybrid duplexes, and is practically inactive towards single-stranded (ss) DNA or single or double-stranded RNA. Moreover, the enzyme is capable to discriminate between perfectly and nonperfectly matched short DNA duplexes. DSN is widely used for full-length enriched cDNA normalization (Zhulidov et al., 2004; Bogdanova et al., 2011a) and for construction of normalized RNA-seq libraries for next generation sequencing ((Christodoulou et al., 2011), Illumina DSN normalization protocol). The list of approved DSN applications also includes normalization of genomic DNA (Shagina et al., 2010), cDNA depletion and ribosomal cDNA depletion (Bogdanova et al., 2009; Bogdanova et al., 2011b; Yi et al., 2011), cDNA subtraction (Peng et al., 2008), SNP detection (Shagin et al., 2002; Liu et al., 2011), construction of repeat-free FISH probes (Swennenhuis et al., 2012), multiplexed fluorescence detection of miRNAs (Yin et al., 2012), quantitative telomeric overhang determination (Zhao et al., 2008; Zhao et al., 2011), etc.