![]() Two chromatids of a chromosome repulse each other with the microtubules remaining stationary and under tension.įigure: Anaphase.Their centromeres of the sister chromatids occupy the plane of the equator forming a metaphase plate, and the arms remain directed towards the poles.During metaphase, the chromosomes are shortest and thickest.By the end of prometaphase, the sister chromatids are attached to the spindle fibers on the opposite ends and are held on the metaphase plate.įigure: Metaphase.At this stage, the chromosomes are violently rotated and oscillated back and forth between the spindle poles because their centromeres are capturing the ends of microtubules and are being pulled by the captured microtubules.Prometaphase is initiated with the breakdown of the nuclear envelope, which enables the interaction of spindle fibers with the chromosomes.However, in some primitive classes of plants and animals, the nuclear envelope does not dissolve during mitosis.įigure: Prometaphase.Lastly, during prophase, the nucleolus gradually disintegrates, and this marks the end of prophase.In the meantime, two pairs of centrioles surrounded by microtubules radiating in all directions migrate to opposite poles of the cell.Similarly, the chromosomes approach the nuclear envelope, causing the central space of the nucleus to become empty.As prophase progresses, the chromatids become shorter and thicker, and two sister chromatids of each chromosome are held together by a special DNA-containing region, called the centromere.The chromosome in the prophase is composed of two coiled filaments, the chromatids, which are the result of the replication of DNA during the S phase.During prophase, the cell becomes spheroid while the cytoplasm becomes more refractile and viscous and pale.Prophase is the first stage of mitosis which is characterized by the appearance of thin-thread like condensing chromosomes.By the end of this phase, the cell enters the division or M-phase of the cell cycle.įigure: Prophase.Cell division involves the enormous expenditure of energy, thus cell stores ATP in the G 2.During this phase, the synthesis of RNA and proteins required for the cell continues.G 2 phase is termed the second gap phase or resting phase of the interphase.Thus, at the end of the S phase, each chromosome has two DNA molecules and a duplicate set of genes.įigure: Late G 2. ![]() ![]() The replication of cytoplasmic DNA can take place at any phase in the cell cycle.
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