![]() ![]() Other microtubules called nonkinetochore microtubules grow from each centrosome toward the center of the cell without attaching to chromosomes. Each chromosome becomes connected to both poles of the spindle. The nuclear envelope disappears, and the spindle fibers attach to the kinetochores of the chromosomes. The cell will eventually divide at a right angle to the spindle axis. ![]() The centrosomes move toward opposite ends of the cell, forming spindle fibers between them. For simplicity, we’ll observe mitosis in a cell with four chromosomes. Prophase begins as the chromatin condenses into visible chromosomes and the nucleolus disappears. Mitosis is divided into four stages called prophase, metaphase, anaphase, and telophase. Assembly of the spindle begins in G2, as the centrosome replicates and tubulin is synthesized. Microtubules arrays called asters radiate from the centrosomes bracing the centrioles during spindle retraction. ![]() In animal cells, centrosomes contain a pair of organelles called centrioles that help organize the spindle. Spindle fibers are assembled by microtubule-organizing center called centrosomes located at the ends of the spindle. This modular nature allows the fibers to lengthen and shorten through the addition and removal of tubulin sub-units. The microtubules of the spindle are called spindle fibers, which consist of repeated tubulin sub-units arranged end-to-end. It’s function is extremely dependent on its function. The mitotic spindle is an array of microtubules responsible for the precise distribution of chromosomes to the daughter cells. Within the centromere is a region called a kinetochore, which functions as an attachment site for the mitotic spindle. The two copies of the duplicated chromosomes are called sister chromatids and are linked at a region of the chromosome called the centromere. Early in mitosis, the chromatin condenses, making the chromosomes visible. During interphase, chromosomes are extended and can’t be seen under the light microscope. Mitosis is required to precisely distribute the duplicated sets of chromosomes to the daughter cells.Įukaryotic chromosomes are made of chromatin, which consists of DNA wrapped around histone proteins. If the cell simply divided in half, each daughter cell would receive a random assortment of chromosomes. Why does a eukaryotic cell need to undergo the specialized process of mitosis? After S phase, there are two complete sets of chromosomes. Hippocampus Biology: Mitosis and Cytokinesis ![]()
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