Agarose Gel Electrophoresis of products of amplification of PreMBT cDNA with exon-specific primers. cDNA was prepared from total RNA extracted from pre-MBT embryos. Aliquots of the cDNA samples were ampified in 2 rounds of PCR with the indicated exon-specific nested primers and with β-actin specific primers. Aliquots of 5'RACE clone plasmid DNA were also amplified. The amplification products were subjected to electrophoresis through a 1.5% agarose gel, stained with ethidium bromide, and photographed under UV light using a digital camera. PMBT = pre-midblastula transition.