Humber Admissions Practice Test

Which of the following accurately describes prophase in mitosis?

1. Chromosomes condense and become visible

2. Chromosomes separate and move to opposite poles

3. Chromosomes are replicated

4. Formation of the nuclear envelope

The correct answer is: Chromosomes condense and become visible

Prophase is the stage of mitosis where several critical changes occur in the cell's structure. During this phase, chromosomes undergo condensation and become visible under a microscope. This visibility is pivotal because it marks the transition from the loosely organized chromatin found in interphase to the tightly packed chromosome structure necessary for the subsequent phases of mitosis. In prophase, the nucleolus disappears, and the mitotic spindle begins to form from the centrosomes. The spindle fibers play an essential role in later stages of mitosis where they will help in the alignment and separation of chromosomes. However, it is specifically the condensation of chromosomes into distinct and observable entities that defines this phase. The other options provided refer to different phases of mitosis. Chromosomes separating and moving to opposite poles occurs during anaphase, chromosome replication takes place during the S phase of interphase before mitosis begins, and the formation of the nuclear envelope occurs in the final stage of mitosis, known as telophase. By focusing on the unique characteristic of prophase, it is clear why the selection accurately describes this crucial step in the mitotic process.