Final answer:
The poly-A tail is a post-transcriptional modification added to the 3' end of pre-mRNAs that enhances mRNA stability and assists in ribosome binding and protection against degradation. The 7-methylguanosine cap is another modification that protects the 5' end and aids translation. Both are crucial for the longevity and functionality of mRNA in eukaryotic cells.
Step-by-step explanation:
The type of eukaryotic post-transcriptional modification that enhances stability and is crucial for ribosome binding, while preventing degradation by exonucleases at one end, is the addition of the poly-A tail. This modification is added to the 3' end of pre-mRNA transcripts and consists of a long chain of adenine nucleotides. The poly-A tail plays a significant role in protecting mRNA from degradation by exonucleases and assists in the export of mRNA from the nucleus to the cytoplasm. Similarly, another modification known as the 7-methylguanosine cap is added to the 5' end of pre-mRNA, providing protection from degradation and aiding in the translation process.
Together, these modifications ensure the stability of mRNA by guarding against exonuclease activity and enhancing the translation efficiency by facilitating the proper binding of ribosomes. RNA stability is also influenced by the length of the poly-A tail, with a longer tail generally increasing the lifespan of the mRNA molecule in the cytoplasm, thus allowing for more protein production.