Agarose Gel Electrophoresis of products of amplification of cDNA with β-Actin primers. cDNA was prepared from aliquots of total RNA samples extracted from embryos, larvae and adult zebrafish as described in methods. Aliquots of the cDNA were diluted 1:100 and 1:1000 prior to amplification with β-actin specific primers. The actin primers span three introns. Genomic zebrafish DNA, diluted 1:50 to approximately 100 ng/μl, was also amplified to confirm that the amplification products are derived from cDNA. The primer sequences are provided in the method section. The amplification products were subjected to electrophoresis through a 1.2% agarose gel, stained with ethidium bromide, and photographed under UV light using a digital camera. PMBT = pre-midblastula transition. 16 Som = 16 somite stage. 5d = 5 days post-dertilization. The dilution factors are indicated at the bottom of the panel. The large amount of amplification product in the 1:100 samples led to smearing and "rabbit-earing".