Question

Which of the following is not true for anaphase? (a) Golgi body and ER are reformed (b) Spindle poles move further apart (c) Chromosomes move to opposite poles (d) Centromeres split and chromatids separate

Short answer

(a) Golgi body and ER are reformed is the false statement. These organelles do not reform during anaphase but during telophase.

Step-by-step solution

Identify true statements

First, let's confirm the true statements. In anaphase, the centromeres do indeed split causing the sister chromatids (duplicate copies of a single chromosome) to separate. These chromatids (now called chromosomes) move to opposite poles, which is facilitated by the spindle poles moving apart.

Identify false statement

Now, option (a) states that the Golgi body and ER are reformed during anaphase. However, these organelles do not reform during anaphase, but in telophase, which is the final stage of cell division. ER and Golgi apparatus disintegrate at the beginning of mitosis and reassemble during telophase after the chromosomes have separated.

Key concepts

Anaphase

Anaphase is a critical stage in the process of mitosis, which is the division of a parent cell into two daughter cells. During anaphase, several key events occur that ensure the proper division of the cell's genetic material. The most significant event in anaphase is the splitting of centromeres. The centromeres are the parts of a chromosome where the chromatids, which are the duplicate copies, are held together. Once the centromeres split, each chromatid, now an individual chromosome, moves toward opposite ends of the cell.
The movement of chromosomes in anaphase is facilitated by microtubules, which are thread-like structures that form part of the cell's cytoskeleton. The shortening of these microtubules pulls the chromosomes apart. It is essential for the genetic material to be evenly distributed between the two forming daughter cells. This ensures that each daughter cell will have an exact copy of the genetic information from the parent cell.

Mitosis

Mitosis is a form of cell division that results in two genetically identical daughter cells from a single parent cell. It consists of several phases: prophase, metaphase, anaphase, and telophase, which occur in a sequential order. Each stage has its own specific events and roles in the overall process of cell division.
Prophase marks the beginning of mitosis, during which the chromatin condenses into visible chromosomes and the nuclear membrane dissolves. Following prophase is metaphase, where chromosomes align at the cell's equatorial plate. Anaphase is the subsequent stage, characterized by the separation of chromatids to opposite poles. Finally, telophase occurs where the cell begins to divide, the nuclear membranes reform, and chromosomes de-condense back into chromatin. After telophase, cytokinesis takes place, which is the division of the cytoplasm, completing the cell division process.
This orderly sequence of stages ensures that each new cell receives an accurate and complete set of chromosomes.

Chromosome Separation

Chromosome separation is a vital event in cell division, specifically during the anaphase stage of mitosis. The accuracy of this process is crucial as it prevents genetic imbalances in daughter cells. In anaphase, the chromatids, which are previously duplicated chromosomes, are pulled apart into two sets.
The separation is driven by the mitotic spindle, a structure composed of microtubules. These microtubules attach to the centre of each chromosome, known as the centromere, applying forces that draw the chromosomes apart. The precise mechanism ensures that each daughter cell receives one copy of each chromosome.
Errors in chromosome separation can lead to conditions such as aneuploidy, where cells have an abnormal number of chromosomes. This underlines the importance of a reliable chromosome separation mechanism during mitosis.

Spindle Poles

Spindle poles are critical components during the processes of mitosis and chromosome separation. They are regions at opposite ends of the cell where spindle fibers originate. These fibers, made from microtubules, reach out to attach themselves to chromosomes.
In anaphase, the spindle poles play a significant role as they move further apart, helping pull the chromosomes to opposite sides of the cell. This movement ensures that the chromosomes are distributed evenly between the two developing daughter cells.

• Originating from the centrosomes, spindle poles provide the necessary tension and force required for chromosome segregation.
  
• They ensure that proper cell division takes place by coordinating the movement of chromosomes.
  

The correct function of spindle poles is vital for successful cell division, safeguarding the integrity of cellular reproduction.

Golgi Apparatus

The Golgi apparatus is a key organelle involved in processing and packaging proteins and lipids within the cell. Although it is not directly involved in the mechanics of cell division, it undergoes significant changes during the mitotic process.
At the onset of mitosis, including anaphase, the Golgi apparatus disassembles. This allows the cell's structural resources to be focused on the critical task of dividing the chromosomes. The Golgi apparatus reforms during telophase, the final stage of mitosis, after the separation of chromosomes is complete. The reformation is essential for the cell to regain its full functional capacity as the division concludes.

• It ensures the newly divided cells can resume their roles in processes like protein synthesis and cell membrane maintenance.
  
• Understanding its behavior during cell division helps clarify how cells prepare and recover from mitosis.
  

By reorganizing after mitosis, the Golgi apparatus plays its part in returning the cell to normal functioning post-division.