What is the role of the 5' cap and poly(A) tail in mRNA?

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The main idea is that the 5' cap and the poly(A) tail stabilize mRNA and promote its export and translation. The 5' cap, added early in transcription, protects the mRNA from 5' exonuclease degradation and serves as a recognition site for initiation factors that recruit the ribosome to start protein synthesis. The poly(A) tail, added after transcription, increases mRNA stability, aids in export from the nucleus to the cytoplasm, and interacts with binding proteins to help circularize the mRNA, which enhances translation efficiency and ribosome recycling. Together, these features keep mRNA intact long enough to be translated and optimize how well it is used by ribosomes. Statements claiming they degrade mRNA, encode amino acids, or signal DNA replication don’t fit, because neither cap nor tail is a coding sequence and they aren’t involved in replication signaling.