Metáfase

Metáfase refers to a stage in the cell division process, specifically during meiosis and mitosis. It occurs after the prophase and before the anaphase. During this phase, the chromosomes condense, become more compact, and are fully visible due to the shortening of the chromosome arms and the condensation of the chromatin fiber.

In meiosis, the metáfase stage is crucial for the process of pairing chromosomes, a process known as synapsis. This pairing is necessary for the exchange of genetic material between homologous chromosomes through a process called crossing over. In addition, during the metáfase stage, the homologous pairs are held together by a protein structure called the synaptonemal complex, which facilitates the pairing and exchange of genetic material.

In mitosis, the metáfase stage is characterized by the alignment of the paired sister chromatids, which are identical copies of the DNA, along the metaphase plate of the spindle apparatus. The metaphase plate is an imaginary plane where the sister chromatids separate and move to opposite poles of the cell, each carrying a complete set of chromosomes. Prior to the onset of anaphase, the chromosomes at the metaphase plate are in a stable equilibrium, with those attached to each pole being balanced by a similar number of chromosomes attached to the opposite pole.

In both meiosis and mitosis, the precise length of time the cell spends in the metáfase stage is crucial for proper chromosome separation and cell division. This is where the cell organizes the separation of identical sister chromatids into two separate entities. In cells where mitosis alone occurs for both the somatic and germ cells, this specific segmentation allows the cells to divide accurately.