Repeated sequences copy number, determination

Several of the purple-membrane-containing extreme halophiles (i.e., Halobacterium salinarium and its close relatives) contain small, high-copy-number plasmids, whose DNA sequences have been determined. The sequences are quite similar, and all have an open reading frame of about 1 kbp and a set of hexanucleotide repeats that may be involved in the maintenance of the plasmid [23-25]. 

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