Final answer:
The three main post-transcriptional modifications in eukaryotes are 5' capping, polyadenylation, and splicing. 5' capping protects the mRNA and is important for translation initiation, polyadenylation protects the mRNA and aids in nuclear export, and splicing removes non-coding regions and joins coding regions to create a translatable mRNA sequence.
Step-by-step explanation:
The three post-transcriptional modifications often seen in the maturation of mRNA in eukaryotes are: polyadenylation, 5' capping, and splicing. These modifications are crucial for the conversion of a primary RNA transcript into a mature mRNA molecule that is ready for translation into a protein.
- 5' Capping involves the addition of a 7-methylguanosine cap to the 5' end of the RNA molecule. This cap protects the mRNA from degradation and is a recognition site for ribosomes to initiate translation.
- Polyadenylation is the process of adding a poly-A tail, which consists of a chain of adenine nucleotides, to the 3' end of the RNA transcript. The poly-A tail protects the mRNA from degradation and aids in its export from the nucleus to the cytoplasm.
- Splicing is the removal of introns - non-coding regions - from the RNA transcript, linking exons - coding regions - together to form the final mRNA sequence that will be translated into protein.
The sequence in which these modifications occur is splicing, 5' capping, and polyadenylation. It's important to note that only mature mRNAs that have undergone these modifications are exported from the nucleus to the cytoplasm for protein synthesis.