What occurs during early prophase of mitosis?

• A. Replication of DNA
• B. Spindle formation
• C. Breaking down of the nuclear envelope
• D. Chromosome alignment

Answer: (C)

During early prophase of mitosis, one of the key events is the breakdown of the nuclear envelope. This step is crucial as it marks the transition from interphase, where the genetic material is loosely organized, to a period where the chromosomes become more compact and organized. As the prophase progresses, chromatin condenses into distinct chromosomes that can be easily seen under a microscope. The dismantling of the nuclear envelope facilitates the interaction between chromosomes and the spindle apparatus that forms later in mitosis.

While spindle formation begins during prophase, that process becomes more prominent in later stages. Replication of DNA occurs during the S phase of interphase, prior to prophase, so it is not a feature of early prophase. Chromosome alignment primarily happens in metaphase, which follows prophase, rather than in early prophase. Hence, the breakdown of the nuclear envelope is a defining characteristic of early prophase.