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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<http://en.wikipedia.org/wiki/RNA_interference>
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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>
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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>
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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>