CHO 세포를 재료로 ENU와 MNU를 여러농도로 처리한후 시간 경과에 따른 염색체 이상율을 조사하여 다음과 같은 결과를 얻었다. (1) ENU와 MNU에 의한 염색체 이상 빈도는 처리 후 시간의 경과와 농도에 따라 상이한 현상을 나타냈다. (2) ENU 처리군에서는 염색체 이상형은 염색분체 절단이 대부분이었으나 고농도군 ($10^-3 M$)에서는 처리 후 24시간에 염색분체 교환이 염색분체 절단을 능가하였다. (3) MNU 처리군에서는 염색체 이상형은 염색분체 절단이 대부분이었으나 $10^-4$ M 이상에서는 처리후 12시간부터 염색분체 교환이 염색분체 절단을 능가하였다.
Chromosome aberrations induced by ENU and MNU were investigated in CHO cells at various doses and times after treatment. The results obtained were as follows: The frequency of chromosome aberrations induced by ENU and MNU drastically depends on the length of the post-treatment period and the concentration of these chemicals. In ENU-treated groups, the major type of aberration was chromatid deletions in earlier samples but the frequency of chromatid exchanges increased with time, revealing, predominant type at 24 hours after treatment with $10^-3$ M. In MNU-treated groups, chromatid deletions were also major type but frequency of chromatid exchanges were predominant from 12 hours after treatment with $10^-4$ and $10^-5$ M.
