Which of the following is the correct sequence of events during mitosis?
A) Chromosomes split, nuclear membrane dissolves, nuclear membrane forms, chromosomes line up
B) Nuclear membrane forms, chromosomes line up, chromosomes split, nuclear membrane dissolves
C) Nuclear membrane dissolves, chromosomes line up, chromosomes split, nuclear membrane forms
D) Chromosomes line up, nuclear membrane forms, nuclear membrane dissolves, chromosomes split
The correct answer and explanation is :
The correct answer is:
C) Nuclear membrane dissolves, chromosomes line up, chromosomes split, nuclear membrane forms
Explanation (300 words):
Mitosis is the process by which a eukaryotic cell divides its nucleus and genetic material to form two identical daughter cells. It occurs in a precise sequence of events to ensure that each new cell receives an exact copy of the parent cell’s DNA. The correct order of events in mitosis ensures proper cell division and genetic consistency.
- Nuclear membrane dissolves (Prophase to Prometaphase): Mitosis begins with the breakdown of the nuclear envelope. This allows the spindle fibers, which have formed from the centrosomes, to access the chromosomes. During this phase, the chromosomes condense and become visible under a microscope.
- Chromosomes line up (Metaphase): Next, the chromosomes align themselves along the metaphase plate—an imaginary line equidistant from the two spindle poles. Each chromosome’s centromere is attached to spindle fibers coming from opposite poles of the cell.
- Chromosomes split (Anaphase): The centromeres divide, and the sister chromatids (previously joined chromosomes) are pulled apart by the spindle fibers toward opposite poles of the cell. This separation ensures that each daughter cell will receive an identical set of chromosomes.
- Nuclear membrane forms (Telophase): As the chromatids reach the poles, a new nuclear membrane forms around each set of chromosomes. The chromosomes begin to decondense back into chromatin. This marks the near end of mitosis.
Finally, cytokinesis (not part of mitosis but follows it) divides the cytoplasm, resulting in two separate cells.
Understanding the correct order of mitotic phases is essential in biology and medicine, especially in fields like cancer research where abnormal cell division plays a critical role.