RNA Interference

Why does control of gene expression usually occur at the transcription stage rather than the translation stage? Protein synthesis is a two stage process. DNA is used to produce mRNA (transcription) and then mRNA is used to produce proteins (translation). Transcription factors are a wide variety of molecules that control the production of mRNA. Factors that control the rate of translation are less well known – one is described in this animation. Unlike DNA, messenger RNA is a relatively short-lived molecule. If it is not used then it will probably break down shortly. Controlling the production of mRNA rather than its use, once produced, is probably a more efficient use of cellular resources.

View the animation below, then complete the quiz to test your knowledge of the concept.


1	RNA intereference is a mechanism for silencing gene expression at the

		A)	level of replication.
		B)	level of transcription.
		C)	post-transcriptional but pre-translational level.
		D)	level of translation.
		E)	post-translational level.

2	The protein ________ acts as an endonuclease in the first step of RNA interference.

		A)	interferon
		B)	phaser
		C)	sizer
		D)	dicer
		E)	vader

3	RNA interference is stimulated in the presence of ________ in the cell.

		A)	single-stranded RNA
		B)	double-stranded RNA
		C)	single-stranded DNA
		D)	double-stranded DNA
		E)	proteins

4	RISC is an RNA-protein complex that binds to cellular mRNAs.

		A)	True
		B)	False

5	Antisense mRNA can be produced during the life cycle of all viruses.

		A)	True
		B)	False

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