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Replication patterns of DNA in the chromosomes of barley, rye, and durum wheat were examined by an immunological method with an anti-5-bromodeoxyuridine (BrdU) antibody. In barley metaphase cells, basically five types of chromosome replication were observed. They were characterized by replication signals in (i) proximal regions, (ii) proximal and interstitial regions, (iii) whole chromosomes, (iv) interstitial and distal regions, and (v) distal regions. These replication patterns appeared to change from type (i) to type (v) as the incubation duration after BrdU treatment increased. This suggests that in barley, chromosome replication generally starts in the distal regions and proceeds to the proximal regions. In rye and durum wheat chromosomes, however, it was suggested from similar observations that the replication commenced in the interstitial regions and, through replication in the proximal regions, ended up in the distal regions. C-bands tended to replicate late in the chromosomes of barley and rye, but this was not the case in durum wheat. These results suggest that in each species the timing of replication may be controlled simultaneously over a rather wide chromosomal area in each chromosome. |
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