Final answer:
At the end of one generation time, the chromosomes will look like they have been replicated, with each chromosome consisting of two identical chromatids attached at the centromere.
Step-by-step explanation:
When cultured mammalian cells are placed in culture in the presence of BrdU and allowed to divide for one generation time, the chromosomes will look like they have been replicated. At the end of one generation, each chromosome will consist of two identical chromatids attached at the centromere, forming an X-shaped structure called a replicated chromosome. This is the characteristic appearance of chromosomes in the S-phase of the cell cycle, when DNA replication occurs.