While it is relatively easy to define what a hurricane or earthquake is, defining a drought is more subjective. Droughts do not have the immediate effects of floods, but sustained droughts can cause economic stress throughout an area. The word drought has various meanings, depending on a person's perspective.
For the software package, see Partition function for Interacting RNAs. Piwi-interacting RNA (piRNA) is the largest class of small non-coding RNA molecules expressed in animal cells. piRNAs form RNA-protein complexes through interactions with piwi proteins.
The structure of RNA. RNA is a type of nucleic acid called ribonucleic acid 1  : The RNA nucleotides [nucleotide: a molecule built from a nitrogenous base (base containing nitrogen), a 5-carbon sugar (a pentose sugar) and a phosphate group] are joined to form a single strand.he structure of RNA. RNA is a type of nucleic acid called ribonucleic acid 1  : The RNA nucleotides [nucleotide: a molecule built from a nitrogenous base (base containing nitrogen), a 5-carbon sugar (a pentose sugar) and a phosphate group] are joined to form a single strand.