Figure 10.6: Transcription of a Eukaryotic Gene The β-globin gene diagrammed here is 1,733 base pairs (bp) long. The three exons contain codons (see Concept 10.3) for 147 amino acids plus a stop codon signaling the end of translation. The two introns (noncoding sequences containing almost 1,000 bp between them) are initially transcribed but then are spliced out of the pre-mRNA transcript.