When BrdU incorporates into DNA replication very late, only a few light-stained bands can be found near the terminal or middle area of some chromosomes.

• 至S期DNA合成晚期掺入BrdU，最终染色体出现以深染带纹为主，浅染带纹仅出现于少数染色体的中部、近中部或端部的晚复制带。