[Cause of the change in the type of structural chromosomal mutations in the cell transition from the G1 to the S phase].

Cessation of exchange interactions among chromosomes and change of the chromosome type of aberrations for chromatid type were found on the model of the Crepis capillaris germinating seeds sychronized with 5-fluor-2-desoxyuridine at the end of G1-beginning of S-phase and then exposed to X-ray irradiation.