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Practice English Speaking&Listening with: mRNA Splicing

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Key factors in this process include:

possessing introns and exons

and the spliceosome.

Here we see an RNA molecule with a single intron.

Several signals exist within the intron

that are used in the splicing process.

From the 5' end of the intron, these are,

GU,

the A branch site,

a pyrimidine-rich region,

and the 3' AG.

The GU and AG sequences

define the beginning and end of the intron.

Splicing is mediated by the spliceosome,

which consists of several protein-RNA complexes.

The first step involves two complexes that bind near the GU sequence.

The RNA is then looped,

and three other protein-RNA complexes bind.

This final complex

then undergoes a conformational change.

Introns are non-coding RNA sequences that must be removed before translation.

The process of removing the intron is called splicing.

The intron is then cleaved at the 5' GU sequence

and forms a lariat at the A branch site.

The 3' end of the intron is next cleaved at the AG sequence,

and the two exons are ligated together.

As the spliced mRNA is released from the spliceosome,

the intron debranches, and is then degraded.

The Description of mRNA Splicing