Which of the following does not occur during mitosis?
Select one:
a. spindle formation
b. separation of sister chromatids
c. separation of the spindle poles
d. condensation of the chromosomes
e. replication of the DNA
The Correct Answer and Explanation is :
The correct answer is e. replication of the DNA.
Explanation:
Mitosis is the process of cell division that ensures each daughter cell receives an identical set of chromosomes. It is divided into several stages, each with distinct events that prepare the cell for division.
- Spindle Formation: Spindle fibers are structures made of microtubules that form during mitosis. These fibers are crucial for the movement and separation of chromosomes. Spindle formation begins during prophase and continues into metaphase, where the chromosomes align.
- Separation of Sister Chromatids: In anaphase, the sister chromatids (the two identical halves of a duplicated chromosome) are pulled apart toward opposite poles of the cell. This ensures that each daughter cell will receive a complete set of chromosomes.
- Separation of the Spindle Poles: During mitosis, especially in anaphase, the two spindle poles (which are formed by centrioles in animal cells) move further apart, assisting in the separation of chromosomes. This occurs as the mitotic spindle expands and elongates.
- Condensation of the Chromosomes: Early in prophase, the chromatin (a complex of DNA and proteins) condenses into visible chromosomes. This condensation allows for the chromosomes to be more easily separated during later stages of mitosis.
However, replication of the DNA does not occur during mitosis. DNA replication occurs during interphase, which is the phase preceding mitosis. Specifically, DNA is replicated during the S phase of interphase, where the entire genome is copied to prepare for mitosis. After DNA replication, the cell enters the G2 phase, where it prepares for mitosis by synthesizing proteins and organizing structures like the spindle.
Thus, the correct answer is e because DNA replication happens before mitosis starts, not during it.