What occurs to the nucleolus and nuclear membrane during mitosis?

During mitosis, specifically during prophase, the nucleolus and the nuclear membrane undergo significant changes as the cell prepares to divide. The nuclear membrane breaks down to allow the spindle fibers to access the chromosomes, which have already condensed and become visible. The nucleolus, responsible for ribosomal RNA synthesis, also disappears at this stage.

As the cell progresses into telophase, these structures begin to reform. The nuclear membrane reassembles around each set of separated chromosomes at opposite poles of the cell, and the nucleolus reappears within the newly formed nuclei. This process is crucial for ensuring that the genetic material is properly encapsulated in the resultant daughter cells.

The other choices do not reflect the actual events of mitosis accurately. For example, stating that both structures remain intact throughout the process ignores the dynamic changes that occur during prophase. Similarly, the idea that they migrate to opposite sides or are duplicated prior to prophase does not align with the established sequence of events in mitosis. Thus, the correct choice clearly outlines the crucial changes that occur to the nucleolus and nuclear membrane during the phases of mitosis.