Fig. 6. RT-PCR on RNA obtained from amphioxus embryonic stages. 12, 15, 18 and 21 refer to hours after fertilisation at 25°C.–, negative control; C, Amphi-hairyC positive control; E-H, Amphi-hairyE to Amphi-hairyH positive controls. The expected size and the name of the amplified bands are indicated. Amphi-hairyE (A), Amphi-hairyF (B), Amphi-hairyG (C) and Amphi-hairyH (D) are not expressed during those stages or are expressed at undetectable levels. For Amphi-hairyH the positive control gives a larger size than the expected in the RT-PCR as the oligonucleotides for Amphi-hairyH expand over two small introns, and the template for the positive control is a plasmid containing genomic regions.