85px|Dicer enzyme
RNA interference (RNAi) is a system within living cells that takes part in controlling which genes are active and how active they are. Two types of small RNA molecules – microRNA (miRNA) and small interfering RNA (siRNA) – are central to RNA interference. RNAs are the direct products of genes, and these small RNAs can bind to other specific RNAs (mRNA) and either increase or decrease their activity, for example by preventing a messenger RNA from producing a protein. RNA interference has an important role in defending cells against parasitic genes – viruses and transposons as well as gene expression in general. The RNAi pathway is found in many eukaryotes and is initiated by the enzyme Dicer (pictured), which cleaves long double-stranded RNA (dsRNA) molecules into short fragments of ~20 nucleotides that are called siRNAs. Each siRNA is unwound into two single-stranded (ss) ssRNAs, namely the passenger strand and the guide strand. The passenger strand is degraded, and the guide strand is incorporated into the RNA-induced silencing complex (RISC). The selective and robust effect of RNAi on gene expression makes it a valuable research tool, both in cell culture and in living organisms because synthetic dsRNA introduced into cells can induce suppression of specific genes of interest. (more...)
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_______________________________ Today's selected anniversaries:
1034:
After Malcolm II of Scotland died at Glamis, Duncan, the son of his second daughter, instead of Macbeth, the son of his eldest daughter, inherited the throne to become the King of Scots. http://en.wikipedia.org/wiki/Malcolm_II_of_Scotland
1863:
American Civil War: Confederate forces were defeated at the Battle of Missionary Ridge in Chattanooga, Tennessee, opening the door to the Union's invasion of the Deep South. http://en.wikipedia.org/wiki/Battle_of_Missionary_Ridge
1917:
World War I: German troops invaded Portuguese East Africa in an attempt to escape superior British forces to the north and resupply from captured Portuguese materiel. http://en.wikipedia.org/wiki/Battle_of_Ngomano
1952:
Agatha Christie's mystery play The Mousetrap, the play with the longest initial run in history, opened at the Ambassadors Theatre in London. http://en.wikipedia.org/wiki/The_Mousetrap
1975:
Upon Suriname's independence from the Netherlands, Johan Ferrier became its first president. http://en.wikipedia.org/wiki/Johan_Ferrier
_____________________________ Wiktionary's word of the day:
importune (v): 1. To harass with persistent requests. 2. To approach to offer one's services as a prostitute http://en.wiktionary.org/wiki/importune
___________________________ Wikiquote quote of the day:
The battle to save life is still going on. … This battle to save life will eventually be won. … Blind faith in established experience has been shattered, outmoded regulations have been smashed. --Ba Jin http://en.wikiquote.org/wiki/Ba_Jin