During prophase , chromatids are condensed into chromosomes , exhibiting short and thick thread-like structures. These chromosomes are aligned in the equatorial plate of the cell by the formation of a spindle apparatus. Spindle apparatus is composed of three components: spindle microtubules, kinetochore microtubules, and kinetochore protein complexes.
The kinetochore protein complexes are attached to the centromeres of each chromosome. All the microtubules in a cell are controlled by two centrosomes arranged at the opposite poles of the cell, forming the spindle apparatus. Spindle microtubules are connected to each of the two centrosomes by their two ends. Kinetochore microtubules, starting from one centrosome, are attached to the centromere through the kinetochore protein complex.
During metaphase , kinetochore microtubules are contracted, aligning the individual bivalent chromosomes on the cell equator. Tension is generated on the centromere which holds the two sister chromatids together at the anaphase by further contracting the kinetochore microtubules.
This tension leads to the cleavage of cohesin protein complexes in the centromere, separating the two sister chromatids apart, producing two daughter chromosomes. During telophase , these daughter chromosomes are pulled towards the opposite poles by the contraction of the kinetochore microtubules. After completing the mitotic phase, parent cell undergoes cytoplasmic division, resulting in genetically identical two separated cells.
The cytokinesis is initiated at the late anaphase. During cytokinesis, organelles, along with the cytoplasm, is divided between two daughter cells by the cell membrane in an approximately equal manner. Plant cell cytokinesis takes place through the formation of a cell plate in the middle of the parent cell.
Animal cell cytokinesis takes place by the cleavage furrow formed by the cell membrane. The difference between plant and animal cell cytokinesis is the requirement of a formation of new cell wall surrounding the plant cell.
A single, but critical checkpoint can be identified. It is known as the metaphase checkpoint since it takes place at the late metaphase. During the metaphase checkpoint, the aligning of all individual, bivalent chromosomes on the cell equator is checked.
The metaphase checkpoint allows the equal segregation of chromosomes between daughter cells. After the DNA is copied and there's a complete extra set of all the genetic material, the cell moves into the G2 stage, where it organizes and condenses the genetic material, or starts to condense the genetic material, and prepares to divide.
The next stage is M. M stands for mitosis. This is where the cell actually partitions the two copies of the genetic material into the two daughter cells. Mitosis is a process of nuclear division in eukaryotic cells that occurs when a parent cell divides to produce two identical daughter cells. During cell division, mitosis refers specifically to the separation of the duplicated genetic material carried in the nucleus. Mitosis is conventionally divided into five stages known as prophase, prometaphase, metaphase, anaphase, and telophase.
While mitosis is taking place, there is no cell growth and all of the cellular energy is focused on cell division. During prophase, the replicated pairs of chromosomes condense and compact themselves.
The pairs of chromosomes that have been replicated are called sister chromatids, and they remain joined at a central point called the centromere.
Interphase is often included in discussions of mitosis, but interphase is technically not part of mitosis, but rather encompasses stages G1, S, and G2 of the cell cycle.
Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nuclear membrane dissolves, marking the beginning of prometaphase. Spindle fibers align the chromosomes along the middle of the cell nucleus. The paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Chromatids arrive at opposite poles of cell, and new membranes form around the daughter nuclei.
In animal cells, cytokinesis results when a fiber ring composed of a protein called actin around the center of the cell contracts pinching the cell into two daughter cells, each with one nucleus. Mitosis animation k.
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