Actin gene number in the sea star Pisaster ochraceus

Abstract

The number of actin genes per haploid genome of the three sea star species has been measured by reassociation of a single-strand actin-coding sequence probe with excess genomic DNA. Least-squares fit analyses of the reassociation curve indicate five actin genes for Pisaster ochraceus and Pisaster brevispinus and eight actin genes for Dermasterias imbricata. Using 3'' untranslated sequence probes from cDNAs or 3'' noncoding regions of a genomic clone, essentially all of the actin-containing Southern digest fragments can be assigned to the three actin gene classes described earlier for P. ochraceus. Through analyses of genomic digests and dot blots from P. ochraceus probed with both the actin sequence and 3'' sequence, the copy number of gene class members per genome has also been estimated.