Question

List the modifications to RNA that make it an mRNA in eukaryotes. What are these for?
Who does these?

Answer 1

5? Capping
7-methylguanosine cap is added to the 5? end of pre mRNA.
It protects the nascent mRNA from degradation.

3? Poly-A Tail
Poly-A polymerase adds a approximately 200 A residues, called the poly-A tail.
It protects the pre-mRNA from degradation and signals the export of the cellular factors that the transcript needs to the cytoplasm.

Pre-mRNA Splicing
Introns are removed and degraded while the pre-mRNA is still in the nucleus.
The splicing of pre-mRNAs is conducted by complexes of proteins and RNA molecules called spliceosomes.