Chromosomes lining up at the equator is an event of Metaphase, not Prophase or Prometaphase, which includes other preparatory changes such as nuclear envelope breakdown and spindle fiber formation.
The event that does not occur during Prophase (which includes prometaphase) is 'chromosomes line up at the equator of the cell'. This is a characteristic event of Metaphase, not Prophase. During Prophase, key processes include the breakdown of the nuclear membrane, the condensation of chromatin into chromosomes, the formation of spindle fibers by the centrioles, and the attachment of spindle fibers to the kinetochores of chromosomes.
In contrast, the precise alignment of chromosomes at the cell's equator is a hallmark of Metaphase, where the chromosomes are organized for subsequent separation into daughter cells. Understanding these stages is critical for students learning about cell division and the intricacies of mitosis.
The statement 'chromosomes line up at the equator of the cell' represents an event from Metaphase, not from Prophase or Prometaphase.