After transcription begins, several steps must be completed before the fully processed mrna is ready to be used as a template for protein synthesis on the ribosomes. which three statements correctly describe the processing that takes place before a mature mrna exits the nucleus?

Poly-A tailing at 3' end

Capping at 5 ' end

Removal of Introns

Explanation:

Post transcription processing includes

1. Poly-A Tailing at 3'end: The 3'end terminus is polyadenlated in the nucleoplasm. This poly-A tail may be from 20-250 nucleotide long. This tail protects mRNA from attack by 3'exonuclease.

2. Capping at 5' end: Eukaryotic mRNAs are all capped at the 5' terminus by 7-methyl guanosine triphosphate. This occur in the nucleus.

3. Removal of Introns: the primary transcript contains coding region (exons) and non coding region (Introns). They intron are cleaved and exons are spliced. This is also done in the nucleus.

currents is the correct answer.