Fig. 3. Expression of MyoD, myogenin, myf5 and MRF4 transcripts in adult tissues of S. macrurus by RT-PCR analysis. Total RNAs from skeletal muscle, EO, liver and brain were reverse transcribed and used for PCR. PCR products (1.0 µg per lane) were resolved on agarose gels containing ethidium bromide, and the resultant bands are presented as negative images of the original gels. Partial cDNA fragments of MyoD (290 bp), myogenin (312 bp), myf5 (209 bp) and MRF4 (301 bp) were detected in skeletal muscle and EO, but not in liver or brain. Control reactions without reverse transcriptase (No RT lanes) were carried out for muscle (lane 2), EO (lane 4), liver (lane 6) and brain (lane 8) to ensure that PCR products were RNA dependent and not the result of genomic DNA amplification. RT-PCR analysis of glyceraldehyde dehydrogenase (GAPDH) was used as a loading control. Lanes labelled M represent the 1 kb⁺ DNA ladder.