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. A large structure called the mitotic spindle also forms from long proteins called microtubules on each side, or pole, of the cell.
During prometaphase, the nuclear envelope that encloses the nucleus breaks down, and the nucleus is no longer separated from the cytoplasm. During anaphase b , the sister chromatids are pulled apart and move toward opposite poles of the cell.
Figure Detail. After metaphase is complete, the cell enters anaphase. During anaphase, the microtubules attached to the kinetochores contract, which pulls the sister chromatids apart and toward opposite poles of the cell Figure 3c.
At this point, each chromatid is considered a separate chromosome. Figure 4: During telophase, two nuclear membranes form around the chromosomes, and the cytoplasm divides. Finally, once anaphase is complete, the cell enters the last stage of the division process — telophase. During telophase, the newly separated chromosomes reach the mitotic spindle and a nuclear membrane forms around each set of chromosomes, thus creating two separate nuclei inside the same cell.
As Figure 4 illustrates, the cytoplasm then divides to produce two identical cells. Why is mitosis important? As previously mentioned, most eukaryotic cells that are not involved in the production of gametes undergo mitosis.
These cells, known as somatic cells , are important to the survival of eukaryotic organisms, and it is essential that somatic parent and daughter cells do not vary from one another. With few exceptions, the mitotic process ensures that this is the case.
Therefore, mitosis ensures that each successive cellular generation has the same genetic composition as the previous generation, as well as an identical chromosome set. Watch this historic video from to see mitosis in action. Key Questions How do centromeres work? Key Concepts chromosomes replication meiosis.
Topic rooms within Genetics Close. No topic rooms are there. Browse Visually. Other Topic Rooms Genetics. Student Voices. Creature Cast. Simply Science. Green Screen. Green Science. Bio 2. Daughter cells are cells that result from the division of a single parent cell.
They are produced by the division processes of mitosis and meiosis. Cell division is the reproductive mechanism whereby living organisms grow, develop, and produce offspring. At the completion of the mitotic cell cycle , a single cell divides forming two daughter cells. A parent cell undergoing meiosis produces four daughter cells. While mitosis occurs in both prokaryotic and eukaryotic organisms , meiosis occurs in eukaryotic animal cells , plant cells , and fungi.
Mitosis is the stage of the cell cycle that involves the division of the cell nucleus and the separation of chromosomes. The division process is not complete until after cytokinesis, when the cytoplasm is divided and two distinct daughter cells are formed. Prior to mitosis, the cell prepares for division by replicating its DNA and increasing its mass and organelle numbers.
Chromosome movement occurs in the different phases of mitosis:. During these phases, chromosomes are separated, moved to opposite poles of the cell, and contained within newly formed nuclei. At the end of the division process, duplicated chromosomes are divided equally between two cells. These daughter cells are genetically identical diploid cells that have the same chromosome number and chromosome type.
Somatic cells are examples of cells that divide by mitosis. Somatic cells consist of all body cell types , excluding sex cells. The somatic cell chromosome number in humans is 46, while the chromosome number for sex cells is In organisms that are capable of sexual reproduction , daughter cells are produced by meiosis. Meiosis is a two part division process that produces gametes. The dividing cell goes through prophase , metaphase , anaphase , and telophase twice. At the end of meiosis and cytokinesis, four haploid cells are produced from a single diploid cell.
These haploid daughter cells have half the number of chromosomes as the parent cell and are not genetically identical to the parent cell. In sexual reproduction, haploid gametes unite in fertilization and become a diploid zygote. The zygote continues to divide by mitosis and develops into a fully functioning new individual.
How do daughter cells end up with the appropriate number of chromosomes after cell division? The answer to this question involves the spindle apparatus. The spindle apparatus consists of microtubules and proteins that manipulate chromosomes during cell division. Spindle fibers attach to replicated chromosomes, moving and separating them when appropriate. The mitotic and meiotic spindles move chromosomes to opposite cell poles, ensuring that each daughter cell gets the correct number of chromosomes.
The spindle also determines the location of the metaphase plate. This centrally localized site becomes the plane on which the cell eventually divides.
The final step in the process of cell division occurs in cytokinesis. This process begins during anaphase and ends after telophase in mitosis. In cytokinesis, the dividing cell is split into two daughter cells with the help of the spindle apparatus.
In animal cells , the spindle apparatus determines the location of an important structure in the cell division process called the contractile ring.
0コメント