Biology / Unit 6 Bio 1275 short lesson, about 20 seconds
Introns and Exons
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The idea
A eukaryotic gene's pre-mRNA contains exons, the sequences that appear in mature mRNA, interrupted by introns, sequences that must be removed.
In practice
A pre-mRNA with alternating exon and intron segments must have every intron removed before the mRNA can be translated.
Where people slip
Exon and intron names describe a gene's transcript, not its final protein — introns never appear in a translated amino acid sequence.
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