Question

a) Briefly outline how eukaryotic mRNA is processed

b) What is the purpose of each of these processes?

Answer 1

In Eukaryotic mRNA the introns are present along with exonic sequences, these are processed by the splicing mechanism, in this process introns are removed and exons are joined which are ready for expression.

Spliceosome mediated RNA splicing mechanism:-

RNA splicing mechanism is catalysed by the special proteins i.e.ubiquitin U1,U2,U5,U4/U6 snRNP and other components. These proteins are assembled at the branch point, near to the intronic sequence so that it attacks the spice site, thus induces cleavage. The 5'end of the introns which is covalently linked to the A nucleotide

In the later step II, the 3'OH of first exon is joined to the second exon sequence, and introns are released as lariat.

Alternative splicing also done similarly to excise the introns.

B) in Eukaryotic mRNA only introns are present it is essential to spice the introns to make processed mRNA for expression without any intreppution.