Fragmentation and Nondisjunction of Barley Chromosomes After the Treatment of Chloramphenicol and Cycloheximide

Barley root meristematic cells were treated with three antibiotics known as the inhibitors of protein synthesis, i.e., chloramphenicol (CAP), cycloheximide (CH) and puromycin (PU), at each stage of the interphase in first cell cycle. The results indicated that both CAP and CH induced the chromosome fragments of dot type after the treatment in early S, late S or early G2 cells, but PU produced no chromosomal aberrations. These chromosome fragments seemed to be produced by a 1-hit event. On the other hand, S cells treated with CAP or CH markedly reduced the number of chromosomes in a cell. The chromosome reduction is likely due to the nondisjunction of chromosomes. Moreover, CH inhibited the protein synthesis as revealed by the incorporation of 3H-lysine, but CAP did not depress at the concentrations used. It was discussed that chromosome fragments are attributable to the chromosome nondisjunction.