Interphase is defined as which of the following?

• A. Nuclear envelope breaks up, allowing spindle to interact with chromosomes
• B. Period of the cell cycle between cell divisions
• C. Chromosomes line up in the middle of the cell
• D. Chromatids separate and move to opposite poles

Answer: (B)

Interphase is the period of the cell cycle between divisions, when the cell is not yet dividing but is actively preparing for it. During this time the cell grows, carries out normal functions, and duplicates its DNA in the S phase, with additional growth and preparation for mitosis in the G2 phase. The nucleus remains intact and chromosomes are not yet condensed, so they aren’t visible as separate structures. This setup ensures mitosis can proceed smoothly once division begins. The events described in the other options—nuclear envelope breaking down and spindle interaction, chromosomes lining up in the middle, and chromatids separating to opposite poles—happen during mitosis, not interphase.