STABILITY OF AN INVERTED REPEAT IN A HUMAN FIBROSARCOMA CELL

Deletions and rearrangements of DNA sequences within the genome of hum an cells result in mutations associated with human disease. We have de veloped a selection system involving a neo gene containing a DNA seque nce inserted into the Ncol site that can be used to quantitatively ass ay deletion of this sequence from the chromosome. The spontaneous dele tion from the neo gene of a 122 bp inverted repeat occurred at a rate of 2.1 x 10(-8) to <3.1 x 10(-9) revertants/cell/generation in three d ifferent cell lines. Deletion of the 122 bp inverted repeat occurred b etween 6 bp flanking direct repeats. Spontaneous deletion of a 122 bp non-palindromic DNA sequence flanked by direct repeats was not observe d, indicating a rate of deletion of <3.1 x 10(-9) revertants/cell/gene ration. This result demonstrates that a 122 bp inverted repeat can exh ibit a low level of instability in some locations in the chromosome of a human cell line.