Final answer:
Introns containing termination codons do not affect protein encoding because they are removed from the pre-mRNA during the RNA splicing process, allowing only the exons to be translated into a functional protein sequence.
Step-by-step explanation:
Introns are known to contain termination codons, but these do not result in the termination of the protein encoded by that gene because they are removed from the pre-mRNA during RNA splicing. Eukaryotic genes consist of exons and introns. The exons are protein-coding sequences, whereas introns, which may contain termination codons, do not encode for proteins. The splicing process ensures that all introns are precisely removed, allowing the exons to join together to code for a functional polypeptide. If introns were not removed or were incorrectly spliced, it would result in a shift in the reading frame, potentially leading to a nonfunctional protein.
During mRNA processing, spliceosomes play a critical role by conducting sequence-specific removal of introns. This process culminates with the mature mRNA, which is free of introns, being transported out of the nucleus for translation into a protein. This is how eukaryotic cells avoid the premature termination of protein translation by intronic termination codons and ensure that only the correct amino acid sequence is synthesized.