Question

During mitosis ER and nucleolus begin to disappear at?

• A. Early prophase
• B. Early metaphase
• C. Late metaphase
• D. Late prophase

Answer 1

The correct option is D

Late prophase

The correct option is D.

An explanation for the correct option:

1. Prophase is a stage of cell division that occurs in both mitosis and meiosis.
2. Prophase is further subdivided into early prophase and late prophase (prometaphase). Two identical chromosomes replicate, forming sister chromatids, and enter prophase from interphase to begin chromosome condensation. As a result, the endoplasmic reticulum and nucleolus are no longer present.

An explanation for the incorrect option:

Option A:

1. Prophase II (prometaphase). The nuclear membrane disintegrates and the chromosomes become totally condensed. The mitotic spindle begins to collect and organize the chromosomes in the late prophase (also known as prometaphase). The chromosomes get even more condensed, resulting in a highly compact structure.

Option B:

1. During the metaphase of mitosis, the chromosomes reach their maximum amount of condensation and become visible under a microscope.
2. The chromosomes are less condensed in early metaphase and become more condensed as the cell proceeds towards the end of metaphase.

Option C:

1. The cell goes through a series of checkpoints in late prometaphase to guarantee that the spindle has formed.
2. Each chromosome is attached to microtubules coming from each side of the cell.
3. As the microtubules retract, equal strain is exerted on the chromosomes from each side of the cell.

Final answer: ER and nucleolus begin to disappear during mitosis during late prophase.