Why do eukaryotic cells need to process mRNA after transcription?

Eukaryotic cells need to process mRNA after transcription primarily to remove non-coding sequences, known as introns, and to facilitate the export of the mature mRNA from the nucleus to the cytoplasm. This processing includes capping at the 5' end, polyadenylation at the 3' end, and splicing, which is the removal of introns and joining of exons. This maturation of mRNA is crucial because only properly processed mRNA can be efficiently translated by the ribosomes into proteins. Additionally, the addition of the cap and tail protects the mRNA from degradation and assists in its recognition by the translation machinery.

While factors such as rapid translation and promoting cell division are important cellular processes, they are not the direct reasons for mRNA processing after transcription. The encoding of additional proteins is also not directly related since the processing primarily pertains to refining the existing mRNA transcript for effective protein synthesis.