Cell Division Definition
In order to divide, cells go through a process called cell division. Depending on the type of organism dividing, there are several types of cell division. Over time, organisms have evolved different and more complex ways to divide their cells. Prokaryotes, or bacteria, divide their cells by binary fission.
Mitosis is used by eukaryotes of all sizes to divide. Eukaryotes that reproduce sexually use a special form of cell division called meiosis to reduce their genetic content. In sexual reproduction, each parent must give only half of the required genetic material, otherwise the offspring would have too much DNA.
Types of Cell Division
Prokaryotic Cell Division
Binary fission is the method of cell division used by prokaryotes to replicate. Prokaryotes are simple organisms with only one membrane and no internal division. In other words, when a prokaryote divides, all it needs to do is replicate its DNA and divide in two. A special protein must first unwind DNA before the process can begin. It is possible for the DNA in prokaryotes to become tangled when it is used by the cell, despite its usual ring structure.
It is necessary to stretch out DNA in order to copy it efficiently. In this way, the two new rings of DNA can also be separated after they have been created. Two strands of DNA separate into two sides of a prokaryote cell. As a result, the cell grows longer and divides in the middle.
It is the DNA that is tangled. Labels are attached to the other components. In binary fission, plasmids are also copied, and can be picked up from dead cells that break apart in the environment. Further replication of these plasmids is possible. A beneficial plasmid will increase in a population if it is beneficial.
Antibiotic resistance in bacteria occurs in part as a result of this process. Proteins are produced by ribosomes, which are small protein structures. Also, they are replicated so that each cell has enough to function.
Eukaryotic Cell Division: Mitosis
The membrane-bound organelles and DNA on chromosomes of eukaryotic organisms make cell division more difficult. DNA, organelles, and cell mechanisms must be replicated before eukaryotes divide. Eukaryotes are believed to have formed by prokaryotes living inside each other, since many of their organelles divide using binary fission.
When DNA and organelles have been replicated during interphase of the cell cycle, the eukaryote can begin mitosis. As the chromosomes condense during prophase, the process begins. DNA would become tangled and break if mitosis did not condense the chromosomes. Many proteins can fold eukaryotic DNA into complex structures.
Chromosomes are lined up in the middle of the cell during metaphase of mitosis. As mitosis proceeds, sister chromatids, which are duplicated copies of each other, are separated into both halves of the cell. A process called cytokinesis divides the cell into two new daughter cells at the end of mitosis.
Mitosis is the process by which eukaryotic organisms divide their cells. Only single-celled organisms use mitosis for reproduction. Almost all multicellular organisms reproduce sexually by combining their DNA with another organism’s. Organisms in these situations require a different method of cell division.
Meiosis produces cells with half of the genetic information of a regular cell, allowing two cells from different organisms of the same species to combine. Mitosis produces identical cells, but meiosis produces cells with half the genetic information as a regular cell.
Eukaryotic Cell Division: Meiosis
In sexually reproducing animals, it is usually necessary to reduce the genetic information before fertilization. Some plants can exist with too many copies of the genetic code, but in most organisms it is highly detrimental to have too many copies. Humans with even one extra copy of one chromosome can experience detrimental changes to their body. To counteract this, sexually reproducing organisms undergo a type of cell division known as meiosis. As before mitosis, the DNA and organelles are replicated.
The process of meiosis contains two different cell divisions, which happen back-to-back. The first meiosis, meiosis I, separates homologous chromosomes. The homologous chromosomes present in a cell represent the two alleles of each gene an organism has. These alleles are recombined and separated, so the resulting daughter cells have only one allele for each gene, and no homologous pairs of chromosomes.
The second division, meiosis II, separated the two copies of DNA, much like in mitosis. The end result of meiosis in one cell is 4 cells, each with only one copy of the genome, which is half the normal number.
Organisms typically package these cells into gametes, which can travel into the environment to find other gametes. When two gametes of the right type meet, one will fertilize the other and produce a zygote. The zygote is a single cell that will undergo mitosis to produce the millions of cells necessary for a large organism. Thus, most eukaryotes use both mitosis and meiosis, but at different stages of their lifecycle.
Cell Division Stages
Depending upon which type of cell division an organism uses, the stages can be slightly different.
Mitosis starts with prophase in which the chromosome is condensed. The cell proceeds to metaphase where the chromosomes are aligned on the metaphase plate. Then the chromosomes are separated in anaphase and the cell’s cytoplasm is pinched apart during telophase. Cytokinesis is the final process that breaks the cell membrane and divides the cell into two.
The stages of meiosis are similar to mitosis, but the chromosomes act differently. Meiosis has two phases, which include two separate cell divisions without the DNA replicating between them. Meiosis I and meiosis II have the same 4 stages as mitosis: prophase, metaphase, anaphase, and telophase. Cytokinesis concludes both rounds of meiosis.
In prophase I, the chromosomes are condensed. In metaphase I, the chromosomes line up across from their homologous pairs. When they are separated in anaphase I and telophase I, there is only one form of each gene in each cell, known as a reduction division. Meiosis II proceeds in the same manner as mitosis, which sister chromatids dividing on the metaphase plate.
By telophase II, there are 4 cells, each with half of the alleles as the parent cell and only a single copy of the genome. The cells can now become gametes and fuse together to create new organisms.
Cell Division is the process by which a parent cell divides into two or more daughter cells. It is essential for growth, development, repair, and reproduction in living organisms.
The two main types of Cell Division are mitosis and meiosis. Mitosis is responsible for the growth and repair of body cells, while meiosis is involved in the production of gametes (sperm and eggs) for sexual reproduction.
Mitosis results in the formation of two genetically identical daughter cells, each having the same number of chromosomes as the parent cell. Meiosis, on the other hand, involves two rounds of cell division and results in the formation of four daughter cells with half the number of chromosomes as the parent cell.
Mitosis consists of four stages: prophase, metaphase, anaphase, and telophase. During prophase, the chromosomes condense, and the nuclear envelope breaks down. In metaphase, the chromosomes align along the equator of the cell. In anaphase, the sister chromatids separate and move towards opposite poles. Lastly, during telophase, the nuclear envelope reforms, and the cell begins to divide.
Cell Division is crucial for several reasons. It allows for the growth and development of organisms by increasing the number of cells. It is involved in tissue repair and regeneration. In sexually reproducing organisms, cell division is necessary for the production of gametes, which are needed for fertilization and the creation of new individuals.