Mitosis Definition
Two new cells are formed during mitosis, the step in the cell cycle when the newly duplicated DNA is separated. The process of asexual reproduction is important for single-celled eukaryotes.
Multicellular eukaryotes undergo mitosis in order to become an entire organism. The other stages in the cell cycle include growth and the replication of DNA, both required for mitosis to take place.
Functions of Mitosis
Development
A multi-celled organism always starts out as a single cell, formed by two gametes. Despite carrying all the DNA necessary to create a fully functioning organism, this zygote lacks nearly enough cells to complete its development. In mitosis, new cells are produced. The first round of mitosis results in only two cells.
Both of these cells undergo mitosis, and there are four of them. It doesn’t take long for the blastula to form, a hollow ball of cells. As more and more cells are created, the ball folds in on itself. As cells differentiate, they are able to perform special tasks in the body. A fully functioning organism is eventually developed and can be born or hatched.
Mitosis is asexual reproduction in single-celled organisms. Mitosis is used by single-celled organisms to reproduce and distribute their DNA. Sexual reproduction is also possible in some single-celled organisms. To reproduce sexually, most organisms undergo another process called meiosis, which reduces their DNA and places it in individual cells. Once these gametes meet, one will become fertilized.
Fertilized gametes contain two sets of genomes, which are necessary for the proper development of most organisms. DNA is only present in one copy in some organisms. These organisms are known as diploids and haploids, respectively.
Replacing Damaged Tissues
Mitosis also functions as a repair mechanism. An organism’s cells are damaged when it is injured. It can be caused by a physical injury, such as a cut, or by environmental factors, such as the sun. Damaged cells must be replaced either way. The pathways that initiate mitosis are activated by nearby cells without sensing their neighbors.
In time, the multiplying new cells reach each other, and the damaged area is covered with new cells. It is possible for some organisms to regenerate entire limbs in this way. Through mitosis, animals such as lizards, crabs, and many others can re-grow their tails and claws.
Phases of Mitosis
Interphase begins and ends mitosis, although technically it is not part of it. In the interphase of the cell cycle, the DNA is duplicated and the cell grows. The cell enters Mitosis after synthesizing its identical DNA set.
Prophase
Prophase is the first stage of mitosis. DNA condenses during prophase. A new strand of DNA is created during interphase when the DNA is in a loose, open form that allows the enzymes to work on it. The chromatin, as it is called, becomes tangled and breaks if the cell moves it without condensing it.
DNA is packaged into very tight packages during prophase by the cell’s machinery, which surrounds it with proteins called histones. It is now possible to move these tight packages of DNA easily. Microtubules are organized on each side of the cell by centrioles, which appear during prophase. Eventually, the microtubules will grab the DNA chromosomes.
Plants proceed to this stage by rearrangement the cell to place the nucleus in the middle. Most of the time, the nucleus of an animal cell is located in the center. Vacuoles containing water often push it to one side in plants. Plants use this preprophase to organize their organelles for division.
Prometaphase
Microtubules are required to reach duplicated chromosomes in order to split them up. Prometaphase is characterized by the breakdown of the nuclear envelope surrounding the cells. DNA was separated from the cytosol of the cell by this membrane. The microtubules extend from the centromeres to the chromosomes when the nuclear envelope dissolves.
A centromere is a special area on each chromosome, and each centromere has a kinetochore. Microtubules attach to these kinetochores, allowing the cell to move chromosomes. During prometaphase, microtubules from each side of the cell attach to each chromosome.
Metaphase
Chromosomes are pulled by microtubules during metaphase. Chromosomes end up in the middle of the cell when both sides pull equally. The metaphase plate is located in this area. There are two copies of DNA aligned on the metaphase plate. The chromosomes line up with their sister chromatids, which are cloned DNA strands. When the microtubules pull the chromosomes apart, each cell gets a functioning genome.
Anaphase
The sister chromatids, identical clones of the same part of DNA, are bound together at their centromeres. During anaphase of mitosis, the proteins that connect these chromatids are destroyed. Each now its own chromosome, the identical halves can be pulled to each cell. In the above picture, there are two white chromosomes and two grey chromosomes.
During anaphase the proteins between the two sister chromatids in each chromosome would dissolve. In the above cell this would lead to 8 total chromosomes after the chromatids separate. In the next phase, they will be separated, to create 4 chromosomes in each cell, the number the cell had before it duplicated its DNA.
Telophase
The final phase of Mitosis, telophase, occurs when the chromosomes are pulled toward each centriole, and a cleavage furrow forms in the cell. The chromosomes will eventually get a nuclear envelope formed around them, and become their own cells. The centrioles will dissolve, and each cell will resume normal functioning.
One crucial last step, cytokinesis, is needed before the cell function. This last process is not a step of mitosis, but rather the beginning of Interphase. Once divided, the cells can resume growing.
Related Biology Terms
- Cell Cycle – In eukaryotes, the cycle consists of Interphase and Mitosis, with some cells going into a non-diving third state.
- Cytoplasm – The fluid surrounding the DNA in cells.
- Microtubules – Small structures in the cytoplasm of cells made from proteins, which allow the cell to move various organelles and chromosomes.
- Binary Fission – The process of cell division in prokaryote, which differs do to the lack of organelles and associated membranes.
FAQ’s
What is mitosis?
Mitosis is a fundamental process of cell division in which a single cell divides into two genetically identical daughter cells. It plays a crucial role in growth, development, and tissue repair in multicellular organisms.
What are the main stages of mitosis?
Mitosis consists of four main stages: prophase, metaphase, anaphase, and telophase. During prophase, the genetic material condenses into visible chromosomes. In metaphase, the chromosomes align along the center of the cell. Anaphase follows, during which the sister chromatids separate and move towards opposite ends of the cell. Lastly, in telophase, two distinct nuclei form around the separated chromosomes.
What is the purpose of mitosis?
The primary purpose of mitosis is to ensure the accurate distribution of genetic material (chromosomes) to daughter cells during cell division. It enables the growth and development of organisms by allowing cells to divide and multiply in a controlled manner.
How does mitosis differ from meiosis?
While mitosis and meiosis are both processes of cell division, they have distinct differences. Mitosis results in the formation of two identical daughter cells with the same number of chromosomes as the parent cell (diploid). In contrast, meiosis involves two rounds of division and produces four genetically unique daughter cells with half the number of chromosomes (haploid) as the parent cell. Meiosis is responsible for the production of gametes (sperm and eggs) and genetic diversity.
What factors regulate the progression of mitosis?
The cell cycle is tightly regulated to ensure accurate progression through mitosis. Key regulatory factors include cyclins and cyclin-dependent kinases (CDKs) that control the timing and progression of cell cycle phases. Checkpoints throughout the cell cycle monitor DNA integrity, chromosome alignment, and other critical factors, ensuring that cells proceed to the next stage only when all requirements are met.