Question

Terminalization occurs during (a) Mitosis (b) Diakinesis (c) Cytokinesis (d) Meiosis II

Short answer

Terminalization occurs during diakinesis.

Step-by-step solution

Understand the terms

Mitosis, diakinesis, cytokinesis, and Meiosis II are all stages of cell division, each with unique characteristics. Terminalization is a process that occurs during the stages of cell division. Thus, it is crucial to understand these biological terms and their processes.

Identify when terminalization occurs

Terminalization occurs during meiosis in the first division. This process is characterized by the gradual disappearance of the chiasmata, starting from the centromere and proceeding towards the telomere.

Match the stage

Based on the information from Step 2, the closest match is 'diakinesis', which is the last stage of prophase I in meiosis. This is where terminalization typically occurs.

Key concepts

Meiosis

Meiosis is a specialized form of cell division that produces reproductive cells, such as sperm and eggs, with half the number of chromosomes of the parent cell. This process consists of two consecutive divisions: meiosis I and meiosis II.

During meiosis I, homologous chromosomes pair up and exchange genetic material through a process called crossing over, forming chiasmata. This exchange increases genetic diversity. Meiosis II resembles a normal mitotic division but further separates the sister chromatids into individual cells. The end result is four genetically distinct haploid cells.

Understanding meiosis is essential for comprehending the concept of terminalization because this process is a critical sub-event of meiosis I, occurring specifically at the diakinesis stage.

Diakinesis

Diakinesis marks the final stage of prophase I in meiosis. During this phase, the chromosomes condense to their maximum extent, and the nuclear envelope begins to break down, preparing the cell for the division. Chromosomes are fully contracted and clearly visible under a microscope.

Diakinesis is significant for terminalization as it is the stage where chiasmata, the visible manifestations of crossover events, move toward the ends of the chromosomes, a phenomenon termed the terminalization of chiasmata. This sets the stage for the accurate segregation of homologous chromosomes to opposite poles.

Cell Division Stages

Cell division is a multipart process that involves several distinct stages. In eukaryotic cells, this division can take the form of either mitosis or meiosis. Mitosis results in two genetically identical daughter cells, while meiosis, as previously described, leads to four genetically unique haploid cells.

The stages of both mitosis and meiosis are complex and include prophase, metaphase, anaphase, telophase, and cytokinesis. Each stage is characterized by specific events and processes that facilitate the proper segregation of chromosomes. The understanding of these stages, especially in meiosis, is crucial to grasp the intricacies of phenomena like terminalization.

Chiasmata

Chiasmata are the X-shaped structures formed at the point where chromosomes (homologues) crossover. These are critical in ensuring genetic recombination—a fundamental mechanism that increases genetic variability within a species.

During the first meiotic division, chiasmata hold the homologues together until anaphase I, ensuring that the chromosomes can segregate accurately. Terminalization, the focal process of our discussion, involves the chiasmata shifting toward the ends of chromosomes during diakinesis, which eventually allows the homologous chromosomes to separate and move to opposite poles of the cell.