The effects of x-rays on the programming of sequential replication of genetic markers have been studied in Bacillus subtilis. Density transfer and transformation techniques were employed to study the replication sequence of eight genetic markers distributed along the chromosome. It was observed that x-rays caused premature gene replication independent of marker position in both stationary and growing cells. The metA region was observed to be particularly sensitive to premature induction of replication. The loss of control of chromosome cycling is best explained by the induction of new starts scattered through the chromosome. These new initiation sites allow limited semiconservative replication and could be the result of x-ray-induced primer sites specific for polymerase(s).

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