Question

What major events occur during anaphase of mitosis?

Short answer

During anaphase of mitosis, major events include the separation of sister chromatids at the centromere, the shortening of spindle fibers facilitated by motor proteins, the movement of chromosomes to opposite poles of the cell, and the continuous elongation of the cell in preparation for telophase. These events ensure equal distribution of genetic material to the two daughter cells.

Step-by-step solution

1. Separation of Chromatids

During anaphase, the sister chromatids are separated at the centromere. The centromere divides, allowing the individual chromatids to be pulled apart. Each separated chromatid is now known as a chromosome.

2. Shortening of Spindle Fibers

As anaphase begins, the spindle fibers attached to the chromatids shorten. This shortening of spindle fibers is facilitated by motor proteins that "walk" along the microtubules, pulling the chromatids towards the opposite poles of the cell.

3. Movement of Chromatids to Opposite Poles

The separated sister chromatids, now called chromosomes, are pulled towards the opposite poles (ends) of the cell. The chromosomes move in a straight line towards the poles due to the shortening of spindle fibers, ensuring that each of the two daughter cells will have equal amounts of genetic material.

4. Continued Elongation of the Cell

While the chromosomes move to opposite ends, the cell continues to elongate. This prepares the cell for the next phase, telophase, where the cell membrane begins to pinch in and create two separate daughter cells. To summarize, the major events during anaphase of mitosis include the separation of sister chromatids, the shortening of spindle fibers, the movement of chromosomes to opposite poles, and the elongation of the cell. These events ensure that the two daughter cells will have identical genetic material.

Key concepts

Separation of Chromatids

Anaphase marks a critical phase in mitosis, where the sister chromatids are intricately separated. Initially, these chromatids are joined at a region called the centromere. As anaphase progresses, the centromeres divide, facilitating the separation of the chromatids. This division transforms individual chromatids into their own distinct entities, now referred to as chromosomes.

By ensuring that each cell receives one copy of every chromosome, the process maintains genetic consistency across the newly formed daughter cells. This accurate division is vital for maintaining genetic integrity during cell division.

Shortening of Spindle Fibers

Spindle fibers play an indispensable role during anaphase by anchoring to the chromatids. These spindle fibers are composed of microtubules, which are dynamic structures capable of rapid assembly and disassembly.

As anaphase commences, the spindle fibers shorten. This shortening doesn't happen randomly but is assisted by motor proteins, which "walk" along the microtubules, effectively pulling the chromatids towards the cell's poles.

• This mechanism ensures swift movement of chromatids.
• It is a finely regulated process that dictates the pace and direction of chromatid separation.

Movement to Opposite Poles

Once the chromatids are released, they move promptly to opposite poles of the cell. This directional movement is facilitated by the pulling action of the spindle fibers.

The chromatids, now called chromosomes, move in a well-organized straight line toward these opposing sides. This meticulous organization ensures that when cytokinesis occurs, each daughter cell inherits an equal amount of genetic material, maintaining cellular function and viability.

• The poles represent the future site of the daughter cells' nuclei.
• The even distribution of chromosomes is essential for genetic stability.

Cell Elongation

Meanwhile, as the chromosomes migrate to the poles, the cell itself undergoes elongation. This continued elongation is the cell's way of preparing for the next phase in the mitotic process, known as telophase.

During elongation, the cell’s shape changes to accommodate the separation of the spindle poles, setting the stage for the eventual division into two cells. This morphing of the cell ensures that, when final division occurs, there is adequate space and resources for each resulting daughter cell.

• Elongation helps in the physical separation of the cell.
• Ensures that the cell is ready for cytokinesis.