Cytokinesis Often, But Not Always, Accompanies _____.
Cytokinesis often but not always accompanies mitosis, which is the process of dividing a parent cell to produce two genetically identical daughter cells.
In cytokinesis, a contractile ring of microfilaments (actin) forms inside the plasma membrane. This ring then contracts, pulling the cell’s equator inward. This creates a cleavage furrow that pinches the cell in half.
During Prophase
Cytokinesis often but not always accompanies prophase, the stage of the cell cycle that involves chromosome condensation and segregation and nuclear division. A single parent cell has four chromatids; two are duplicated to create two daughter cells with the same number of chromosomes (the remaining one is lost in DNA replication).
In animals, the process of cytokinesis entails the formation of a cleavage furrow and contractile ring around the division region. In plant cells, the dividing process is a little different and involves the formation of a cell plate.
When the actin-myosin contractile ring around the cytokinetic furrow contracts, it pinches off the outer surface of the dividing parent cell. This pinching action, which is also referred to as abscission, causes the contractile ring around the parent cell to collapse into two distinct daughter cells, each with its nucleus, organelles, and other cellular components.
However, in some cases, cytokinesis can lead to an unequal distribution of fate-determining molecules between the two daughter cells. This is especially true for developing organisms, where asymmetric cell division occurs.
At this point, a special process called crossing-over takes place that alters the genetic makeup of the chromosomes. Crossing over can change the chromosomes in order to make them more useful for a particular function or to create a cell with a greater capacity for growth or expansion, such as an egg cell in meiosis.
Chromosomes are now arranged in pairs on the kinetochores; the attachment points allow them to move along microtubules and physically interact with the polar microtubules of spindle fibers. The kinetochores reorient themselves, so the chromosomes line up on an equatorial plane. The chromosomes then separate at anaphase and move toward their opposite poles or ends of the cell.
Once the chromosomes are separated, they are no longer visible to the naked eye under a microscope. They will disperse, and new cells will begin to form.
The cell motion during cytokinesis is important for the proper functioning of a eukaryotic taxon. Without it, cells would be unable to replicate and reproduce, so a thorough understanding of cytokinesis is essential to understanding the cell cycle.
During Anaphase
Often but not always, cytokinesis accompanies anaphase, which is the final stage of cell mitosis and the process by which chromosomes are separated from each other. During this phase, the chromatids are separated at their centromeres and then pulled to opposite poles of the dividing cell, thus ensuring that each daughter cell has its own set of identical chromosomes.
During anaphase, the chromosomes are pulled to the opposite poles of the cell by spindle fibers that have been attached to the centromeres. During this time, the spindle forms and grows to the equivalent of twice the size of the metaphase plate (an imaginary line that is equidistant from the chromosomes’ 2 poles).
As the cell progresses through anaphase, the microtubules attached to each chromosome disintegrate. This disintegration is regulated by several processes that are controlled in a sequence.
The first, anaphase A, is characterized by the shortening of kinetochore microtubules that pull chromosomes away from the metaphase plate towards the spindle. This movement is primarily generated by microtubules that are interpolar but also by a subclass of astral microtubules.
Anaphase B, on the other hand, is characterized by the lengthening of polar microtubules that pull chromosomes to the opposing poles of the dividing cell. This movement is primarily generated by microtubules between the chromosomes and the kinetochores that attach them to the centrosomes and astral microtubules that run across the surface of the metaphase plate.
In most eukaryotic cells, anaphase is accompanied by the formation of a membrane that separates the chromosomes from each other and the cytoplasm. This membrane is called the cleavage furrow, formed when a contractile ring of actin filaments contracts inside the plasma membrane at the former metaphase plate.
This ring of actin filaments contracts until it reaches the apex of the anaphase spindle, where it forms a fissure in the apical membrane of the anaphase spindle. This fissure deepens as the contractile ring contracts. The cleavage furrow eventually reaches the anaphase spindle, where its contents – the nucleus and the cytoplasm of the anaphase cell – are separated into two identical daughter cells.
During Telophase
Telophase often but not always accompanies cytokinesis (dividing a cell into two daughter cells). In animal cells, the chromosomes are split and moved from one end of the cell to the other. This process is called karyokinesis, which is the first step of mitosis. In plant cells, the chromosomes are divided into two genetically identical daughter cells through meiosis.
In telophase, the spindle disappears, and a nuclear membrane reforms around each set of chromosomes. A nucleolus reappeared in each new nuclear membrane. Chromosomes begin to decondense and return to their “stringy” form.
During late telophase, the chromatin begins to reform. This is a crucial step in the cell cycle because it allows the cell to enter the next S phase. This is because the chromosomes can begin to bind and associate with multiple protein factors essential for DNA replication. The chromosomes also have the chance to re-establish themselves in the nucleolus, where they can begin the synthesis of proteins from the newly re-formed genetic code.
This is a very important part of the cell cycle because it gives the cell a chance to resume its normal functions. For instance, this is when the cell’s ribosomes can begin to make proteins from the newly synthesized genes.
The chromosomes also re-form and elongate, becoming more scattered and less compact. The microtubules that are tethered to the mitotic spindle continue to elongate, as well.
Once the chromosomes re-form, they become attached and form a dense complex of enzymes, RNA, and DNA called the nucleolus. This complex is responsible for creating many types of proteins from the newly re-formed genome.
In most eukaryotes, the cytokinesis processes in mitosis and meiosis are accompanied by a cellular plate, a thin bridge between the parent and daughter cells. This bridge contains remnants of polar microtubules from the mitotic spindle and is visible under a microscope for hours after telophase has ended.
During Mitotic Phase
Cytokinesis often, but not always, accompanies the mitotic phase, when cells divide to produce two daughter cells. In animal cells, cytokinesis occurs in a pinching of the cell membrane between the developing nuclei. In plant cells, a new cell wall is formed between the two sets of chromosomes.
In this phase of the cell cycle, chromatin in the nucleus begins to condense and become visible under a microscope as chromosomes. Some chromosomes begin to move away from the nucleus, and centrioles begin moving to opposite ends of the cell. Fibers from the centromeres extend across the cell to form the mitotic spindle.
This spindle is a molecular scaffold that holds the chromosomes and helps them to align along the center of the parent cell’s nucleus during metaphase. Chromatids line up at this point to create the metaphase plate, which ensures that each of the daughter cells will get one complete set of chromosomes.
The kinetochores, proteins that attach to the centromeres, then move along the microtubules as the chromosomes orient themselves toward opposite sides of the cell. Some of the chromosomes travel to the poles of the cell, where they meet and form new polar microtubules, and some go back to the central area of the cell, where they are arranged in pairs on the kinetochores.
After this stage of the cell cycle, a ring of contractile filaments binds to the former metaphase plate and pulls the equator of the cell inwards, creating a fissure in the membrane called the cleavage furrow. This furrow deepens as the ring contracts, and eventually, the membrane is cleaved in two (Figure 6.6).
Once the furrow has been created, the additional membrane material is produced via vesicle fusion. This material is inserted next to the contractile ring and is the basis for the cytoplasm that encloses the two daughter cells.
The cytoplasm of the daughter cells is half the volume of the original parent cell. However, the chromosomes in each daughter cell are identical to those of the parent cell.
Cytokinesis Often, But Not Always, Accompanies _____. Best To Know
Cytokinesis is the process that follows nuclear division in eukaryotic cells. It involves the physical separation of the cytoplasm and organelles into two daughter cells, resulting in the formation of two genetically identical cells. Cytokinesis can occur through different mechanisms in different cell types, but it generally involves the formation of a contractile ring that constricts the cell membrane to separate the two daughter cells.
Cytokinesis often, but not always, accompanies the process of mitosis or meiosis, which are the two major types of nuclear division in eukaryotic cells. During mitosis, a single cell divides into two identical daughter cells, each containing the same number of chromosomes as the parent cell. Mitosis is necessary for growth, repair, and asexual reproduction in multicellular organisms. During meiosis, a cell undergoes two rounds of division to produce four haploid daughter cells that are genetically diverse. Meiosis is necessary for sexual reproduction and the production of gametes (sperm and eggs) in animals and spores in plants.
While cytokinesis usually follows nuclear division, there are some exceptions. In some cases, cells can undergo nuclear division without subsequent cytokinesis, leading to the formation of cells with multiple nuclei. This process is known as endoreplication and is observed in some tissues during development or in response to stress. Similarly, some cells can undergo cytokinesis without nuclear division, resulting in the formation of cells with reduced or abnormal chromosomes. This process is known as cytokinesis failure and is associated with genomic instability and cancer.
In summary, cytokinesis is the physical separation of the cytoplasm and organelles into two daughter cells following nuclear division in eukaryotic cells. While it often accompanies mitosis or meiosis, there are exceptions where cells can undergo nuclear division without cytokinesis or vice versa.
FAQ’s
What does cytokinesis accompany?
Every mitosis in a typical cell is accompanied by cytokinesis, although some cells, like vertebrate osteoclasts and Drosophila embryos (described in Chapter 22), go through mitosis without cytokinesis and become multinucleate.
Does cytokinesis usually but not always follow mitosis?
Usually, but not always, cytokinesis comes after mitosis. A cell would divide into two cells without nuclei or one cell with two or more nuclei if it underwent mitosis rather than cytokinesis. unusually tiny nuclei in cells. a cell with one substantial nucleus.
Which is not occurring in cytokinesis of plants?
Plant cells do not go through cytokinesis. The cytoplasm furrows during cytokinesis. A cell plate is used in the process of cytokinesis.
What phase does cytokinesis occur alongside?
After mitosis in the cell cycle is cytokinesis. Cell division occurs during the process of mitosis, which divides the duplicated DNA into two identical daughter cells. Cytokinesis is a component of the final stage of mitosis.
What accompanies telophase in dividing cells?
Once the duplicated, paired chromosomes have been split apart and brought to the cell’s poles, or opposite sides, telophase has begun. To isolate the nuclear DNA from the cytoplasm, a nuclear membrane develops around each set of chromosomes during telophase.
What organelles are involved in cytokinesis?
Plant cells divide into two daughter cells during the process of cytokinesis. Golgi vesicles, which contain the components for the cell wall, are assembled near the equator of the cell and united to form a fluid plate known as the cell plate.
Does cytokinesis usually accompany nuclear division?
The physical process of cell division known as cytokinesis separates a parental cell’s cytoplasm into two daughter cells. It happens simultaneously with the two nuclear division processes known as meiosis and mitosis that take place in animal cells.
