No, DNA is always organized in chromosomes (except in prokaryotes). During mitosis, however, the chromosomes condense considerably, which makes them more visible under the microscope.

@saraccina “Welcome to Fluther. Here’s a good set of images that shows mitosis, step by step and explains what’s going on in each step. In the sequential images starting with Interphase before Mitosis begins, you can clearly see what @gasman is talking about.