Question

The phase of mitosis in which the chromosomes line up at the equatorial plate of the cell is called a. interphase. b. prophase. c. metaphase. d. anaphase. e. telophase.

Short answer

The phase of mitosis in which the chromosomes line up at the equatorial plate of the cell is called \(metaphase\) (option c).

Step-by-step solution

List the phases of mitosis and their main characteristics

To identify the correct answer, we will first list the main characteristics of each phase of mitosis: a. Interphase: This is the phase where the cell prepares to divide, and it is technically not a phase of mitosis. During interphase, the cell grows, replicates its DNA, and prepares for cell division. b. Prophase: In this phase, the chromatin condenses into chromosomes, and the nucleolus disappears. The mitotic spindle starts to form. c. Metaphase: During this phase, the chromosomes line up at the equatorial plate of the cell, and the mitotic spindle is fully formed. d. Anaphase: In anaphase, the sister chromatids separate, and they move towards the opposite poles of the cell. e. Telophase: In this phase, the separated chromatids reach the opposite poles, and the nuclear envelope starts to reform around each set of chromosomes. The chromosomes also start to uncoil, and the nucleolus reappears.

Identify the correct answer

Now that we have listed the main characteristics of each phase, we can easily identify the phase when the chromosomes line up at the equatorial plate of the cell: c. Metaphase So, the correct answer is: The phase of mitosis in which the chromosomes line up at the equatorial plate of the cell is called metaphase (option c).

Key concepts

Metaphase

Understanding the metaphase stage of mitosis is critical to grasping the complexities of cell division. During metaphase, chromosomes, which have already replicated and condensed, align at the center of the cell. This is knownas the metaphase plate or the equatorial plate. The alignment is crucial for the equal distribution of genetic material to each daughter cell following cell division.

At this point, the spindle fibers, originating from opposite spindle poles, attach to the kinetochores of the sister chromatids—these are identical copies of the original chromosome, still held together at a region called the centromere. The tension created by the opposing spindle fibers ensures that chromosomes are poised for separation. When students grasp metaphase’s pivotal role in facilitating the equal sharing of genetic information, they better understand why it is a key point of regulation within cell division.

Cell Division

Cell division is a fundamental biological process allowing organisms to grow, repair tissues, and reproduce. In eukaryotic cells, which include all plant and animal cells, mitosis is the type of cell division that results in two genetically identical daughter cells from a single parent cell. This precise duplication process ensures that each new cell receives an exact copy of the parent cell's genetic material.

Cell division involves a series of tightly coordinated steps: prophase, metaphase, anaphase, and telophase, followed by cytokinesis. Mitosis is under stringent control, with checkpoints that ensure each phase is completed before the next begins. This regulation prevents errors that could lead to disease, such as cancer. The concept exercise enhances understanding of cell division by focusing on identifying and understanding each phase. Students should remember that mitosis is not only about division but also about preserving the integrity of the genetic code across generations of cells.

Chromosome Alignment

Chromosome alignment during metaphase is an exquisite dance of genetic material preparing for separation. This alignment ensures that when the cell divides, each daughter cell inherits a complete set of chromosomes. Disruptions in chromosome alignment can lead to abnormal distribution of chromosomes, a condition known as aneuploidy, which is associated with various genetic disorders and cancers.

Key players in chromosome alignment are the spindle fibers, which form a bridge-like structure between the poles of the cell and the chromosomes. Spindle checkpoint proteins oversee the spindle attachment to the chromosomes, and this checkpoint is a crucial safeguard in the mitotic process. Accurate chromosome alignment is so essential that the cell halts progression to anaphase until all chromosomes are correctly positioned and attached to spindle fibers. By emphasizing the significance of this step, educators can help students appreciate the intricacies of genetic distribution within cellular replication.