Ubi-p63E promoter and 5'UTR sequences are fused upstream of a hybrid reporter composed of mCherry fused via a linker protein to EGFP. The codon usage of the EGFP coding sequence has been modified (by synonymous codon substitutions) so that 100% of the codons correspond to the most rarely used synonymous codon in the D. melanogaster genome. In the mCherry coding sequence, the distribution of codons corresponding to either the most commonly used synonymous codon or 'middle' codons (synonymous codon(s) with a usage frequency in between the rare and most commonly used ones) are mostly clustered together, rather than being in their natural distribution within the coding sequence.