Answer is anaphase
When a dividing eukaryotic cell is treated with a mitotic inhibitor drug, the drug disrupts microtubules. Microtubules are the structures that pull the chromosomes apart when a cell divides. The drug inhibits shortening of spindle microtubules during anaphase stage of mitosis. As a result cell division stops at anaphase stage. Mitotic inhibitors are used in cancer treatment preventing cell from division.
I believe the correct answer is the anaphase of M stage also called Mitosis
The cell cycle of eukaryotes has 4 stages; G1, S, G2 and M phases. It is during the M phase of the cell cycle that there is shortening of the microtubules to pull the separate single chromatids towards different poles so that the cell can undergo cytokinesis (division of the cytoplasm).
Before the cell cycle starts, the cell is usually at rest in a neglidgible G0 phase. It then enters the G1 phase which lasts for around 4 hours. The cell also rests here, prepares and increases the number of organelles. The cell is also checked for any inconsistencies and it does not proceed if errors are found in the DNA. It then enters the S phase where it lasts for around 8 hours and there is doubling of chromosomes in the cell. DNA synthesi occurs. It then proceeds to the G2 phase where again it is checked for any errors and there is increase in organelles.
It is in the M or Mitosis phase of where the cell is considered to be truly dividing. It starts with the prophase stage where the cell prepares for the upcoming division. The chromatin condenses, the nuclear envelope disintergrates and the nucleolus disappears. The spindles begin to disappear in preparation for the next stage of Metaphase. In this stage, the chromatins that had previously been condensed line the equator due to a pull force by kinetochore fibers. Their centromeres then align exactly at the center of the cell. This is the shortest phase of the cycle. Anaphase is the next stage and in this stage, the sister chromatids are pulled on opposite poles by the spindle fibers/microtubules. It is in this stagethat cancer drugs target the cell division by stopping the shortening of these microtubules that pull the chromatins towards different poles. In the last stage called Telophase, the cell is essentially divided and a nuclear envelope forms around each set of chromatin materials on the opposite sides. The cell then undergoes cytokinesis where the cytoplasm pinches and separates forming 2 new daughter cells completing the cell cycle. The cell lasts in this M stage for 11 hours. It enters the G1 phase afresh where it rests and prepares for the next cycle.
Level: High School
Subject: Biology
Topic: Reproduction
