Most cell grow, execute the tasks needed to survive, and also divide tocreate brand-new cells. These an easy processes, known collectively as the cell cycle, are recurring throughout thelife the a cell. Of the assorted parts of the cabinet cycle, the department portion isparticularly important, due to the fact that this is the suggest at i m sorry a cell passes itsgenetic info to that is offspring cells. In many situations, department alsoensures that new cells are easily accessible to replace the older cell within anorganism whenever those cells die.
Prokaryotic cells, which include bacteria, experience a form of cell divisionknown as binary fission. This procedure involves replication the the cell"schromosomes, segregation of the copied DNA, and splitting that the parent cell"scytoplasm. The outcome of binary fission is two brand-new cells that are identical tothe original cell.
In contrast to prokaryotic cells, eukaryotic bio cells might divide via one of two people mitosisor meiosis. Of 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 number of cells — can engage in mitosis. But how doesthis process proceed, and also what kinds of cell does that produce?
During mitosis, a eukaryotic bio cell undergoes a carefullycoordinated nuclear division that outcomes in the formation of 2 geneticallyidentical daughter cells. Mitosis itself consists of five active steps, or phases:prophase, prometaphase, metaphase, anaphase, and telophase. Prior to a cabinet canenter the active phases the mitosis, however, it should go with a duration knownas interphase, during which that growsand to produce the assorted proteins necessary for division. Then, in ~ a criticalpoint during interphase (called the Sphase), the cabinet duplicates that is chromosomes and ensures that is systems are readyfor cell division. If all conditions are ideal, the cell is currently ready come moveinto the very first phase that mitosis.
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Figure 1:During prophase, the chromosomes in a cell"s nucleus condense to the allude that they deserve to be viewed using a light microscope.
Prophase is the first phase ofmitosis. During this phase, the chromosomes inside the cell"s nucleus condensation andform tight structures. In fact, the chromosomes become so dense that theyappear as curvy, dark lines when viewed under a microscope (Figure 1). Becauseeach chromosome was duplicated during S phase, that now is composed of two identicalcopies dubbed sister chromatids that space attached in ~ a usual center point called the centromere.
Important changes additionally take place outside of the cell core duringprophase. In particular, two structures called centrosomes move to opposite political parties of the cell throughout this phaseand start building the mitotic spindle.The mitotic spindle dram a an essential role during the later phases of mitosis together it orchestrates the movement of sister chromatids come opposite poles of the cell (Figure 2).
After prophase is complete, the cabinet enters prometaphase. During prometaphase, thenuclear membrane disintegrates and also the mitotic spindle gains accessibility to the chromosomes. Throughout this phase, a protein structure dubbed the kinetochore is connected with the centromere on every sister chromatid.Stringlike structures dubbed microtubulesgrow out from the spindle and connectto the sisters chromatids at your kinetochores; one microtubule from one sideof the spindle attaches come one sister chromatid in each chromosome, and onemicrotubule native the various other side of the spindle attaches come the various other sisterchromatid (Figure 3a).
In metaphase (a), the microtubules the the spindle (white) have actually attached and also the chromosomes have actually lined up on the metaphase plate. Throughout anaphase (b), the sister chromatids room pulled apart and also move toward opposite poles the the cell.
Following prometaphase, metaphase begins. In ~ the begin of metaphase, the microtubulesarrange the chromosomes in a line along the equator the the cell, known as the metaphase plate (Figure 3b). Thecentrosomes, on the opposite poles that the cell, then prepare to separate the sisterchromatids.
After metaphase is complete, the cabinet enters anaphase.During anaphase, the microtubules attached to the kinetochorescontract, which traction the sisters chromatids apart and also toward oppositepoles of the cell (Figure 3c). At this point, every chromatid isconsidered a separate chromosome.
Figure 4:During telophase, 2 nuclear membranes form around the chromosomes, and also the cytoplasm divides.
Finally, when anaphase is complete, the cell enters the last phase of the department process — telophase.During telophase, the recently separated chromosomes reach the mitoticspindle and a nuclear membrane forms around each set of chromosomes,thus creating two different nuclei within the same cell. As number 4 illustrates, the cytoplasmthen divides to produce two the same cells.
As formerly mentioned, many eukaryotic cellsthat are not connected in the manufacturing of gametes undergo mitosis. Thesecells, known as somatic cells, areimportant to the survival of eukaryotic bio organisms, and it is crucial thatsomatic parent and daughter cells execute not differ from one another. With couple of exceptions,the mitotic procedure ensures that this is the case. Therefore, mitosis guarantee thateach succeeding cellular generation has the same genetic composition as theprevious generation, and also an similar chromosome set.
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