To address whether the observed sequence differences in the 30 UTR of Cyp12d1-d and Cyp12d1-p translate into
expression differences, we measured the absolute levels of Cyp12d1-d and Cyp12d1-d transcript’s abundance in the reference strain y; cn bw sp.We found significant differences in basal expression levels, where Cyp12d1-d, which contains a strong polyadenylation signal, is expressed 140-fold higher than Cyp12d1-p. This suggests that duplication of Cyp12d1 led to the inclusion of a strong polyadenylation signal in the 30 UTR of Cyp12d1-d by duplication of a sequence alreadyื found in the 50 untranslated region (Fig. 3). Thus, even with 99.4 %nucleotide similarity, duplication ofCyp12d1 does not
necessarily produce a double dose of gene expression, as even seemingly slight changes in the 30 UTR affect transcript
abundance.