Most cells grow, do the tasks needed come survive, and also divide tocreate brand-new cells. These simple processes, known jointly as the cabinet cycle, are repetitive throughout thelife the a cell. That the assorted parts of the cabinet cycle, the department portion isparticularly important, due to the fact that this is the allude at i beg your pardon a cell passes itsgenetic information to that is offspring cells. In many situations, department alsoensures that brand-new cells are easily accessible to replace the older cells within anorganism anytime those cell die.
Prokaryotic cells, which incorporate bacteria, experience a kind of cabinet divisionknown together binary fission. This procedure involves replication the the cell"schromosomes, segregation of the duplicated DNA, and also splitting the the parent cell"scytoplasm. The result of binary fission is two brand-new cells the are similar tothe initial cell.
In contrast to prokaryotes cells, eukaryotic cells may divide via either mitosisor meiosis. The these two processes, mitosis is much more common. In fact, whereasonly sexually reproducing eukaryotes have the right to engage in meiosis, every eukaryotes —regardless of size or variety of cells — deserve to engage in mitosis. Yet how doesthis procedure proceed, and also what species of cells does the produce?
During mitosis, a eukaryotic bio cell experience a carefullycoordinated nuclear division that results in the formation of two geneticallyidentical daughter cells. Mitosis itself consists of five active steps, or phases:prophase, prometaphase, metaphase, anaphase, and telophase. Before a cell canenter the energetic phases the mitosis, however, it need to go v a period knownas interphase, throughout which the growsand produces the miscellaneous proteins necessary for division. Then, in ~ a criticalpoint throughout interphase (called the Sphase), the cell duplicates that chromosomes and ensures the systems are readyfor cell division. If all conditions are ideal, the cell is currently ready to moveinto the very first phase the mitosis.
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Figure 1:During prophase, the chromosomes in a cell"s nucleus condensation to the allude that they have the right to be perceived using a irradiate microscope.
Prophase is the an initial phase ofmitosis. Throughout this phase, the chromosomes within the cell"s nucleus condense andform tight structures. In fact, the chromosomes come to be so thick that theyappear as curvy, dark lines once viewed under a microscopic lense (Figure 1). Becauseeach chromosome was copied during S phase, that now is composed of 2 identicalcopies dubbed sister chromatids that room attached at a common center allude called the centromere.
Important changes additionally take place external of the cell nucleus duringprophase. In particular, two structures dubbed centrosomes move to opposite political parties of the cell throughout this phaseand begin building the mitotic spindle.The mitotic spindle plays a an essential role throughout the later on phases that mitosis together it orchestrates the movement of sister chromatids come opposite poles the the cabinet (Figure 2).
After prophase is complete, the cell enters prometaphase. During prometaphase, thenuclear membrane disintegrates and also the mitotic spindle gains access to the chromosomes. Throughout this phase, a protein structure called the kinetochore is associated with the centromere on each sister chromatid.Stringlike structures called microtubulesgrow out from the spindle and connectto the sister chromatids at your kinetochores; one microtubule from one sideof the spindle attaches come one sister chromatid in every chromosome, and onemicrotubule native the other side of the spindle attaches come the various other sisterchromatid (Figure 3a).
In metaphase (a), the microtubules of the spindle (white) have attached and also the chromosomes have lined increase on the metaphase plate. During anaphase (b), the sister chromatids are pulled apart and move towards opposite poles of the cell.
Following prometaphase, metaphase begins. In ~ the start of metaphase, the microtubulesarrange the chromosomes in a line along the equator that the cell, known as the metaphase plate (Figure 3b). Thecentrosomes, on the opposite poles of the cell, then prepare to different the sisterchromatids.
After metaphase is complete, the cabinet enters anaphase.During anaphase, the microtubules attached to the kinetochorescontract, which pulls the sister chromatids apart and also toward oppositepoles that the cabinet (Figure 3c). In ~ this point, each chromatid isconsidered a different chromosome.
Figure 4:During telophase, 2 nuclear membranes form around the chromosomes, and the cytoplasm divides.
Finally, when anaphase is complete, the cabinet enters the last phase of the department process — telophase.During telophase, the newly separated chromosomes reach the mitoticspindle and also a nuclear membrane forms around each set of chromosomes,thus creating two separate nuclei inside the same cell. As number 4 illustrates, the cytoplasmthen divides to create two the same cells.
As previously mentioned, many eukaryotic cellsthat room not involved in the production of gametes experience mitosis. Thesecells, recognized as somatic cells, areimportant come the survive of eukaryotic organisms, and it is important thatsomatic parent and also daughter cells execute not vary from one another. With couple of exceptions,the mitotic procedure ensures that this is the case. Therefore, mitosis guarantee thateach successive cellular generation has actually the same genetic composition together theprevious generation, and an similar chromosome set.
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