Repetitive DNA sequence from the crayfish Procambarus clarkii.

A repetitive DNA element was obtained from a crayfish genomic library while attempting to isolate the gene for the pigment concentrating hormone (PCH) with an oligonucleotide probe. The probe was directed to the coding region of the octapeptidic hormone deduced from the amino acid sequence of PCH (1). The isolated clone contained a 14 nucleotide sequence tandemly repeated 30 times; eleven nucleotides of the repeat were identical to a region of the probe. Dot blot hybridization of genomic DNA with the purified insert shows that there are approximately 100 copies per genome. Preliminary Southern blot experiments indicate that the repeat is dispersed throughout the genome. The isolated clone comprises the following sequence: