Final answer:
Eukaryotic pre-mRNA is modified through the addition of a 5' cap and poly-A tail and through splicing to remove introns before it is ready for translation into a protein in the cytoplasm.
Step-by-step explanation:
During the process of transcription, an mRNA molecule is synthesized from a DNA template. In eukaryotic cells, this pre-mRNA undergoes several modifications before it can be translated into a protein on the ribosome. One of the first modifications is the addition of a 5' methylguanosine cap at the beginning of the transcript. This cap aids in the protection of mRNA from degradation and is recognized by the translational machinery.
Another modification is the addition of a poly-A tail at the 3' end of the mRNA which also contributes to mRNA stability and facilitates its export from the nucleus. Additionally, the mRNA undergoes splicing, where non-coding regions called introns are removed and coding regions called exons are joined together. The splicing process ensures that only the necessary coding information is contained within the mature mRNA. Only after these modifications—which include 5' capping, 3' polyadenylation, and splicing—is the mRNA ready to be transported out of the nucleus and into the cytoplasm for translation.