Question

The individual chromosomes become visible with a light microscope during which stage of mitosis? a. prophase b. prometaphase C. metaphase d. anaphase

Short answer

The individual chromosomes become visible with a light microscope during the prophase stage of mitosis.

Step-by-step solution

Brief description of mitosis stages

Mitosis is a process where a single cell divides into two identical daughter cells. It consists of four main stages: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Let's briefly describe each stage.

Prophase

During prophase, the first stage of mitosis, the genetic material inside the cell's nucleus condenses and becomes visible as individual chromosomes. The nucleolus disappears, and the mitotic spindle begins to form.

Metaphase

In metaphase, the second stage of mitosis, the chromosomes align at the cell's equator. The mitotic spindle is fully formed and connects to the centromeres of the chromosomes, making sure they will be divided equally.

Anaphase

Anaphase, the third stage of mitosis, is characterized by the separation of sister chromatids. The mitotic spindle pulls the chromatids to opposite poles of the cell, ensuring each daughter cell receives an equal amount of genetic material.

Telophase

During telophase, the final stage of mitosis, the chromosomes arrive at the poles of the cell and begin to decondense. The mitotic spindle disappears, and nuclear envelopes reform around the chromosomes, resulting in two separate nuclei inside the cell.

When do chromosomes become visible?

As we can see from the descriptions above, individual chromosomes become visible with a light microscope during prophase, as the genetic material inside the nucleus condenses. So, the correct answer to the exercise is: a. prophase

Key concepts

Prophase

Prophase is the initial stage of mitosis, during which several key processes occur that set the stage for successful cell division. At the start of prophase, the chromatin within the nucleus starts to condense. This condensation marks the visibility of individual chromosomes under the light microscope.
As the chromatin condenses, these chromosomes become massively more dense, and each consists of two sister chromatids joined at the centromere.

• The nucleolus fades away, disappearing from view.
• The mitotic spindle begins to form from microtubules. This structure will be responsible for moving the chromatids apart later in mitosis.

Prophase is essential as it transforms chromatin into structured chromosomes, allowing for easy segregation later in the cycle.

Stages of Mitosis

Mitosis is the process of cell division that results in two identical daughter cells from a single parent cell. It is divided into several distinct stages, each with its own key activities.

• Prophase: The chromatin condenses, chromosomes become visible, and the mitotic spindle begins to form.
• Metaphase: Chromosomes align along the cell's equatorial plane, attached to spindle fibers.
• Anaphase: The centromeres split, and sister chromatids are pulled to opposite poles, guided by the spindle fibers.
• Telophase: Chromatids reach the poles and begin to decondense, nuclear envelopes reform, and the cell prepares to divide.

This ordered sequence ensures that each daughter cell receives the exact genetic material necessary to function properly.

Cell Division

Cell division is a fundamental biological process by which a parent cell divides into two or more daughter cells. It is vital for growth, tissue repair, and reproduction in living organisms. Mitosis is one type of cell division that results in two genetically identical diploid cells.

• Growth and Repair: In multicellular organisms, cell division is crucial for growth and replacing damaged or dead cells.
• Reproduction: Asexual reproduction in some organisms relies on mitosis to produce offspring that are genetically identical to the parent.

Cell division through mitosis is carefully regulated to ensure proper genetic distribution and cellular function in organisms.

Chromosome Visibility

Chromosome visibility is a significant phenomenon during mitosis, providing insight into the genetic material's organization and separation. During interphase, chromosomes are not clearly visible under a light microscope because the DNA is loosely packed as chromatin. However, as mitosis begins:

• In prophase, chromosomal visibility starts as chromatin condenses into distinguishable chromosomes.
• This visibility is essential for ensuring accurate chromosome alignment and segregation.

The clear observation of chromosomes during prophase allows scientists and students to study the behavior of chromosomes during cell division, contributing significantly to our understanding of genetic transmission.