Characterisation of 5S rDNA in Gasterosteus aculeatus (Teleostei, Gasterosteidae)

The 5S rRNA genes of Gasterosteus aculeatus were characterised. Genomic DNA was amplified by PCR using two primers constructed in different salmonid s pecies in order both to extract the total 5S rDNA (coding region + nontrans cribed spacer region) and to generate amplified DNA products only if 5S rDN As were tandemly arrayed. Amplification revealed four bands (A, B, C, and D ) of about 250, 370, 580, and 660 base pairs, respectively. The electrophor etic pattern yielded by PCR products appeared very similar in the various s pecies examined, it was also present in a selachian, an amphibian and a rep tile. However, differences were observed in the size of the bands. Band A w as cloned and sequenced: it consisted of 225 base pairs (A+T = 48.6%; G+C = 51.4%) and showed a high sequence homology to 5S rDNA in many vertebrate s pecies. Hybridization on nylon filters of genomic DNA digested with several restriction enzymes showed the typical tandem array of repeated DNAs.