The cell has divided, and the two identical cells are now ready to begin their first period of growth. The changes now taking place are the reverse of those that occurred during prophase: the chromosomes uncoil, new membranes form around the nuclei, and the fibers of the spindle disappear. In the last phase-telophase-the cell divides. Each chromosome is made up of duplicate chromatids (the products of DNA replication) joined at their centromeres.
In this way a complete set of chromosomes migrates toward each centriole. Prophase During prophase, the strands of chromatin, which are highly extended during interphase, shorten, thicken and resolve themselves into recognizable chromosomes. Once the chromatids separate, they are called chromosomes. As the third phase-anaphase-begins, the chromatids separate and move to opposite ends of the cell. The second phase of mitosis is metaphase, in which the chromosomes move into the equatorial plane of the spindle. Many of these from one centriole join with strands from the other to form the spindle. From the centrioles, long, thin strands extend in all directions. The long, threadlike material of the nucleus coils up into visible chromosomes, and the nuclear membrane disappears. Near the end of Prophase I, the homologous chromosomes begin to separate. In the first phase-prophase-a centriole, located outside the nucleus, divides. Mitosis maintains the cells original ploidy level (for example, one diploid 2n. The process of mitosis is continuous, but it is possible to identify four general phases, each characterized by specific activity. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.
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