Post-transcriptional modification converts eukaryotic pre-mRNA into mature mRNA by capping, adding a poly-A tail and splicing introns before translation begins.
Coverage 2013–2023 · Updated 16 Jul 2026
Eukaryotic pre-mRNA is processed by adding a 5' cap and poly-A tail and removing introns so mature mRNA can be exported and translated.
Processing protects RNA, supports export and helps ribosomes recognize the message. Exons are joined in the order defining the coding sequence.
Trace: pre-mRNA; cap and tail; intron removal; exon joining; mature mRNA export.
Removing an intron prevents its sequence from being read as part of the final translated message.
Processing changes RNA, not the original DNA sequence; different processing choices can alter the final protein.
This objective is assessed through multiple choice.
Build the answer around this relationship: Eukaryotic pre-mRNA can contain both introns and exons.
Saying introns are added during processing rather than removed.
Representative question
What happens to mRNA after transcription in eukaryotic cells?
Binding to the large subunit of the ribosome
Removal of introns
Addition of exons
Attachment of an amino acid
RNA polymerase reads template DNA 3' to 5' and synthesizes RNA 5' to 3'; ribosomes translate mRNA codons in the 5' to 3' direction. Promoters mark transcription start regions and orientation; transcription factors help RNA polymerase bind and initiate in eukaryotes. Non-coding DNA does not code for polypeptide amino acid sequences and includes introns, regulatory sequences, telomeres, rRNA genes, and tRNA genes. Eukaryotic pre-mRNA is modified before export and translation by adding a 5' cap and poly-A tail and removing introns by splicing. Alternative splicing joins different exon combinations from one pre-mRNA, so one gene can produce multiple protein variants in different cells or stages. Translation initiation assembles ribosomal subunits at the start codon AUG; initiator tRNA enters the P site and A, P, and E sites organize tRNA movement. Newly made polypeptides may be folded, cleaved, or chemically modified; preproinsulin processing to active insulin is a key example. Proteasomes degrade tagged, damaged, or unneeded proteins; amino acid recycling supports new protein synthesis and proteome quality control.
