What is formed during prophase of mitosis?

During prophase of mitosis, several key events occur as the cell prepares to divide. Among these, the formation of spindle fibers is crucial. Spindle fibers are structures made of microtubules that play an essential role in ensuring that chromosomes are accurately segregated to each daughter cell. These fibers begin to extend from the centrosomes, which move to opposite poles of the cell.

The thickening of the cell membrane does not occur during prophase; rather, the focus is on the internal organization of the cell’s components. While chromosomes do coil and condense, the most significant transformational activity associated with spindle fiber development is what highlights prophase. Moreover, chromosome replication is completed before prophase, during the S phase of interphase, so it does not occur during this stage. Thus, the emphasis on spindle fiber formation as a pivotal aspect of prophase demonstrates its importance in guiding chromosomes during the later stages of mitosis.