What is the ideal gas law constant? How do you calculate the ideal gas law constant? How do you find density in the ideal gas law? Does ideal gas law apply to liquids?
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Study guides. Q: What would happen if cytokinesis occurred without mitosis? Write your answer Related questions. What would happen if mitosis cytokinese happened without mitosis?
Mitosis without cytokinesis? What would happen if cytokinesis occurred with mitosis? What would happen to a cell that undergoes repeated mitosis without cytokinesis? What would happen if cytokinesis occurred before mitosis? What would happen to cell if mitosis occurred without cytokinesis? What happen during the cell cycle? How cytokinesis happen? What would happen to the number of chromosomes in a cell if mitosis occurred but cytokinesis did not take place?
What would happen if cytokinesis occurred without replication of DNA? What would happen if the cell went through mitosis but not cytokinesis? What would happen if cytokinesis occurred before telophase was completed? What would happen if a cell completed mitosis but not cytokinesis? What would happen if cytokinesis took place before mitosis?
What is the difference betwen cytokinesis and mitosis? The assembly of the cell plate begins in late anaphase and is guided by a structure called the phragmoplast , which contains the remaining overlap microtubules of the mitotic spindle that interdigitate at their growing plus ends.
This region of overlap is similar in structure to the central spindle in animal cells in late anaphase. Small vesicles, largely derived from the Golgi apparatus and filled with polysaccharide and glycoproteins required for the synthesis of the new cell-wall matrix, are transported along the microtubules to the equator of the phragmoplast , apparently by the action of microtubule -dependent motor proteins.
Here, the vesicles fuse to form a disclike, membrane -enclosed structure called the early cell plate see Figure G. The plate expands outward by further vesicle fusion until it reaches the plasma membrane and the original cell wall and divides the cell in two. Later, cellulose microfibrils are laid down within the matrix of the cell plate to complete the construction of the new cell wall Figure The special features of cytokinesis in a higher plant cell.
The division plane is established before M phase by a band of microtubules and actin filaments the preprophase band at the cell cortex. At the beginning of telophase, after the chromosomes more Procaryotic cells divide by a process called binary fission. The single, circular DNA molecule replicates and division occurs by the invagination of the plasma membrane and the laying down of new cell wall between the two chromosomes to produce two separate daughter cells.
As soon as oriC is replicated, one copy of the sequence is immediately translocated to the opposite pole of the cell, after which the rest of the chromosome is replicated. Like the two spindle-pole asters in an animal cell, the bacterial daughter chromosomes at the cell poles somehow determine the location of the plane of cell division , ensuring that fission takes place at the cell equator, so that each daughter cell inherits one chromosome Figure Although a number of genes and proteins involved have been identified, the mechanisms responsible for the active translocation of oriC and the inhibition of fission everywhere but at the equator remain unknown.
Cell division in the bacterium E. The single, circular chromosome contains an origin of replication called oriC. Before division, the chromosome is polarized, so that oriC is at one pole of the bacterium. As soon as the oriC sequence is copied, more Binary fission in procaryotes depends on filaments made of the FtsZ protein.
FtsZ is a cytoskeletal GTPase that is structurally related to tubulin and assembles into a ring at the equator of the cell Figure A , and see Figure The FtsZ filaments are essential for the recruitment of all the other cell division proteins to the division site. Together, these proteins guide the inward growth of the cell wall and membrane , leading to the formation of a septum that divides the cell into two.
Bacteria in which the ftsZ gene is inactivated by mutation cannot divide. A FtsZ-based mechanism is also used in the division of chloroplasts in plant cells Figure B and mitochondria in protists.
In fungi and animal cells, another self-assembling GTPase called dynamin discussed in Chapter 13 has apparently taken over the function of FtsZ in mitochondrial division. The FtsZ protein. A Fluorescence micrographs showing the location of the FtsZ protein during binary fission in E. The protein assembles into a ring at the center of the cell, where it helps orchestrate cell division. The bacteria here have been more With the evolution of the eucaryotes, the genome increased in complexity, and the chromosomes increased in both number and size.
For these organisms, a more elaborate mechanism for dividing the chromosomes between daughter cells was apparently required. Clearly, the mitotic apparatus could not have evolved all at once. In many primitive eucaryotes, such as the dinoflagellate Cryphthecodinium cohnii, mitosis depends on a membrane -attachment mechanism, in which the chromosomes have to bind to the inner nuclear membrane for segregation.
The intermediate status of this large, single-celled alga is reflected in the composition of its chromosomes, which, like those of procaryotes, have relatively little associated protein.
The nuclear membrane in C. Where these spindle microtubules press on the outside of the nuclear envelope , the envelope becomes indented in a series of parallel channels Figure The chromosomes become attached to the inner membrane of the nuclear envelope opposite these channels, and chromosome segregation occurs on the inside of this channeled nuclear membrane. Kinetochores in this species seem to be integrated into the nuclear membrane and may therefore have evolved from some membrane component.
The use of different chromosome separation mechanisms by different organisms. Some of these may have been intermediate stages in the evolution of the mitotic spindle of higher organisms. For all examples except bacteria, only the central nuclear region more Eucaryotic tubulin and procaryotic FtsZ clearly have a common evolutionary history. But, microtubules are important for chromosome segregation in even the most primitive eucaryotes, where they are also present in flagellar axonemes discussed in Chapter Whether the flagellum or the spindle evolved first is unclear.
A somewhat more advanced, although still extranuclear, spindle is seen in hypermastigotes, in which the nuclear envelope again remains intact throughout mitosis. These large protozoa from the guts of insects provide a particularly clear illustration of the independence of spindle elongation and the chromosome movements that separate the chromatids.
The sister kinetochores become separated by the growth of the nuclear membrane to which they are attached before becoming attached to the spindle. Only when the kinetochores are near the poles of the spindle do they acquire the kinetochore microtubules needed to attach them to the spindle. Because the spindle microtubules remain separated from the chromosomes by the nuclear envelope, the kinetochore microtubules, which are formed outside the nucleus , must somehow attach to the chromosomes through the nuclear membranes.
After this attachment has occurred, the kinetochores are drawn poleward in a conventional manner see Figure Organisms that form spindles inside an intact nucleus may represent a further stage in the evolution of mitotic mechanisms. In both yeasts and diatoms, the spindle is attached to chromosomes by their kinetochores, and the chromosomes are segregated in a way loosely similar to that described for animal cells—except that the entire process generally occurs within the confines of the nuclear envelope see Figure At present, there is no convincing explanation for why higher plants and animals have evolved a mitotic apparatus that requires the controlled and reversible dissolution of the nuclear envelope.
Cell division ends as the cytoplasm divides into two by the process of cytokinesis. During mitosis, a cell duplicates all of its contents, including its chromosomes, and splits to form two identical daughter cells.
The other type of cell division, meiosis, ensures that humans have the same number of chromosomes in each generation. Once mitosis is complete, the entire cell divides in two by way of the process called cytokinesis Figure 1. When cytokinesis finishes, we end up with two new cells, each with a complete set of chromosomes identical to those of the mother cell. Mitosis is the process in which the nucleus of a eukaryotic cell divides.
During this process, sister chromatids separate from each other and move to opposite poles of the cell. Cytokinesis is the final stage of cell division, during which the cytoplasm splits into two and two daughter cells form.
Explain why mitosis has to come before cytokinesis in the cell cycle. Mitosis has to come before because cytokinesis because the chromosomes need to be separated.
Usually, cytokinesis is the last phase in mitosis in which the contents of the cell cytoplasm and nuclei are divided over two separate, identical daughter cells. The result of mitosis without cytokinesis will be a cell with more than one nucleus.
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