How do cells know when to split and reproduce themselves?
115635
DNA contains a complete blueprint for the body, not only for growth but also repair.  Although each cell contains a complete copy of the original DNA, the particular cell is differentiated from the original DNA containing cells at conception and can only make cells of a particular type (blood, skin, bones, brain, etc.).  During growth, cells divide because the blueprint has not been completed.  Much later little growth is required except perhaps hair, skin and gut lining, etc. and DNA splits and reproduces to make repairs (to patch wounds, etc.) to restore the blueprint construction to normal best it can.  Differentiation may occur because particular cells are influenced by surrounding cells.  Therefore a new toe never grows within a damaged eye.
259644
Mitosis produces daughter cells genetically identical to the parent cell.\nThis has to be true since mitosis is the cell division producing growth - we would not expect entirely different bits and pieces to appear as we grew!\n\nThe first stage of mitosis is DNA replication. The following stages share out the exact copies of DNA equally between the daughter cells.
626233
Mitosis allows the chromosomes in a cell to be duplicated so that a new cell can be formed. \nMeiosis uses the same concept except that you end up with four haploid( half the # of chromosomes) gametes, or reproductive cells because of the second half of the meiosis cycle. When these cells(either egg-sperm, pollen-seed, ect) come together, they form a diploid cell(twice the # of chromosomes as the haploid cell), which then has the number of chromosomes needed for the organism to grow and the species continue on. This also results in different combinations of genes, unlike mitosis, so there is some individuality amoung members of that species.
196196
Well, as you may already know, the purpose of both mitosis and meiosis is to take one cell and make two cells. Before the cells do this though, they have to make sure that a few things are in order. Obviously, there has to be enough stuff for the 2 cells to each be able to live independently. so, there has to be duplication of a lot of stuff before the first cell (let's call it the parent) divides. One of these things is the genome. These are the chromosomes which are made up of DNA. Once the DNA replicates (makes 2 copies of everything from what the parent originally had), the cell can divide. There are now 4 chromosomes of each type, we started out with our usual 2 of each (most organisms have 2 of each chromosome and they differ slightly from each other-this becomes important for meiosis), then when everything duplicated, we got 4! \n\nIn MITOSIS, the 2 cells that come out of the division (lets call them the daughters), are EXACTLY the same in genetic makeup as the original mother cell. They have the very same DNA and therefore make the same proteins and therefore the cells behave the same. \n\n In MEIOSIS on the other hand, the cells are not the same at all. And in fact, this is the point of meiosis - to make new types of cells. You may know that eggs and sperm are products of meiosis, but you not only get a mixing of genes from your mother (from the egg) and father (from the sperm), but the genes inside the egg and sperm are pre-mixed because of meiosis. Thus, genetic diversity!, and an explanation for why you have traits given to you from your grandmother through your father, even though your father may not have that trait (he carries it in his genes for later mixing). This may be a complicated issue in itself but since we have 2 of every chromosome and therefore 2 of every gene (even before the DNA replication that preceeds mitosis), there's a chance that the 2 copies of the same gene are different, one of which shows up in your father and one which you have that you got from your grandmother throuh your father. The mixing, by the way comes about because after the DNA replicates in preparation for cell division. This is neat and involves chromosomes breaking apart and joining back together. Take a look at the animated movie of meiosis at http://www.biology.yale.edu/animatedMeiosis.nclk - make a point to notice the red and green chromosomes at the beginning and the mixed ones at the end.
238950
When a cell divides you get a new cell. There are actually four main stages of cell division. They are:\nProphase\nMetaphase\nAnaphase\nTelophase.\n\nIf you want more information, I would suggest trying Wikipedia, or your local library.
606518
one cell divides to two cell and the new cells grow in size and the process repeats itself
241204
During *mitosis*, the cytoplasm of a cell and its organelles separate into two new *identical cells*?\n\nI'm not sure what else you're looking for here...
263412
Reproduction\n\nUnder favorable conditions amebas divide by binary fission (splitting) to produce two daughter amebas, the nucleus dividing by mitosis. When an ameba is divided artificially, the portion containing the nucleus forms a new cell membrane and continues as a whole animal, while the other portion lives only as long as its present food supply lasts, ultimately dying, since it cannot ingest food or reproduce. If conditions are unfavorable, e.g., in the absence of food and water, amebas secrete a firm protective covering and encyst until conditions are again favorable to active division.
80916
============================================================\nMitosis is a special kind of cell division used by eukaryote cells. You will probably find a series of diagrams in your biology text book to show the stages of mitosis; these are:\n\nprophase \nmetaphase \nanaphase \ntelophase \n============================================================\n============================================================\n2. cell division \n\neukaryotic cell \n\na. By mitosis (def).\nb. Sex cells in diploid (def) organisms are produced through meiosis (def). \n\nprokaryotic cell \n\na. Usually by binary fission (def). No mitosis.\nb. Organisms are haploid (def). No meiosis needed. \n============================================================\n\nMore at the links:
283484
ur question should be under biology but still, mitosis is the process of when the cells split to create 4 indentical cells during mitosis, one copy of the dna is distributed into each of the tow daughter cells mitosis id divided into 4 interphases: prophase, metaphase, anaphase, and telophase. in prophase, the chromatin in the nucleus condenses to form chorosomes. structures celled spindle fibers form a bridge between the ends of the cell. the nuclear membrane breaks down. in metaphase, the chromosomes line up across the center of the cell. each chromosome attaches to a spindle fiber at its centromere, which still holds the chromatids together. in anaphase, the centromeres split. the two chromatids separate. one chromatid moves along the spindle fiber to one end of the cell. the other chromatid moves to the opposite end. the cell becomes stretched out as the opposite ends pull apart. in telophase, the chromosomes begin to stretch out and lose their rodlike appearance. this occurs in the two regions at the ends of the cell. a new nuclear membrane forms around each region of chromosomes. o yeah and btw mitosis is on stage of the cell cycle there are like 2 before it and 1 after it
766661
do you mean what processes cells must undergo? \n\nIf that's your question, then the processes would be cell division by mitosis (to produce more cells, so that organism can increase in size/length), cell elongation(this occurs mainly in plants via vacuolation and thus aids in increase in size and length) and cell differentiation(this allows genes to be switched on or off so that certain traits/phenotypes can be expressed, eg. gene that codes for blue eyes switched on for cell in the eye and not elsewhere like cell on the hand/feet). Hope this answers your question.
68378
I think what you're looking for has to do with replication. Every time the cell goes through mitosis to divide, it has to make an exact copy of all the DNA in the cell, so that there are two complete copies, one for each daughter cell. The process of replication and division is the cell cycle.\n\nIn replication, a complex of enzymes copies the DNA by unzipping the double helix to expose the single strands. Someone else mentioned A-T C-G bair pairing and that is correct. The four subunits in DNA are the bases, and they are abbreviated A,T,C and G. Just by the shape of the molecules, A will connect with T and C with G pretty much always (though there are exceptions that are beyond the scope of a general explanation). \n\nSo in replication, enzymes pull the two strands of the double helix apart in short regions, pulling apart the A-T C-G bair pairing. It is energetically unfavorable to have a single strand of DNA exposed and not base paired. Free nucleotides in the cell will come in and form hydrogen bonds with the exposed template strand (it will happen on both strands), and then enzymes will connect the newly deposited bases with phosphodiester linkages to form a new DNA molecule. This forms a new strand of what is called duplex DNA, meaning it is a new double helix. The complementarity of the base pairs drives replication to produce an exact copy of each part of the genetic code. The error rate is very low, but errors can and do occur, and there is proofreading machinery to check for mistakes and excise and replace incorrect base pairs.\n\nPictures are helpful...in the second link, scroll down to see the replication bubble. A replication fork and a replication bubble are essentially the same thing...it's the site where the double helix is open and replication is occurring.
740160
1- Meiosis happens in stem cells that give rise to gametes (sex cells). \nMitosis happens in all other cells.\nIn women every month only one stem cell goes through meiosis forming 4 haploid cells. In men many cells go through meiosis everyday.\nEvery other cell in body goes through mitosis in a daily basis to replace old and dead cell.\n2- Before cell replication starts.\n3- At the end of the prophase (in case of meiosis, end of the prophase 1)\n4- Mitosis: diploid cells; Meiosis: haploid cells\n5- Every thing but cell division: the cell obtain nutrients and when it gets close to cell division, it will duplicate its DNA and other organelles.
1037721
The first cell "must" divide only once but "may" divide almost without end during the life of a creature.  When the first cell divides its DNA splits like cutting the rungs of several (helical) ladders (genes) and each ladder half then regenerates its missing half in the new cells.  After the split, which is the original cell?  If one of the two "new" cells died prematurely, the remaining cell would likely carry on.  After only a few cell divisions, cells differentiate and become specialized and no longer are capable of producing all the tissue types required.  The original cell is lost for practical purposes.
728867
In biology, meiosis is the process that allows one diploid cell to divide in a special way to generate haploid cells in eukaryotes. The word "meiosis" comes from the Greek meioun, meaning "to make smaller," since it results in a reduction in chromosome number.\n\nMeiosis is essential for sexual reproduction. It therefore occurs in most eukaryotes, including single-celled organisms. A few eukaryotes, notably the Bdelloid rotifers, have lost the ability to carry out meiosis and acquired the ability to reproduce by parthenogenesis. Meiosis does not occur in archaea or prokaryotes, which reproduce by asexual cell division processes.\n\nDuring meiosis, the genome of a diploid germ cell, which is composed of long segments of DNA called chromosomes, undergoes DNA replication followed by two rounds of division, resulting in haploid cells called gametes. Each gamete contains one complete set of chromosomes, or half of the genetic content of the original cell. These resultant haploid cells can fuse with other haploid cells of the opposite gender or mating type during fertilization to create a new diploid cell, or zygote. Thus, the division mechanism of meiosis is a reciprocal process to the joining of two genomes that occurs at fertilization. Because the chromosomes of each parent undergo genetic recombination during meiosis, each gamete, and thus each zygote, will have a unique genetic blueprint encoded in its DNA. In other words, meiosis is the process that produces genetic variation.\n\nBiochemically, meiosis uses some of the same mechanisms employed during mitosis to accomplish the redistribution of chromosomes. There are several features unique to meiosis, most importantly the pairing and recombination between homologous chromosomes, which enable them to separate from each other.click here:http://en.wikipedia.org/wiki/Meiosis#History\n\nMitosis is the process by which a cell separates its duplicated genome into two identical halves. It is generally followed immediately by cytokinesis which divides the cytoplasm and cell membrane. This results in two identical daughter cells with a roughly equal distribution of organelles and other cellular components. Mitosis and cytokinesis together is defined as the mitotic (M) phase of the cell cycle, the division of the mother cell into two daughter cells, each the genetic equivalent of the parent cell.\n\nMitosis occurs exclusively in eukaryotic cells. In multicellular organisms, the somatic cells undergo mitosis, while germ cells — cells destined to become sperm in males or ova in females — divide by a related process called meiosis. Prokaryotic cells, which lack a nucleus, divide by a process called binary fission.\n\nBecause cytokinesis usually occurs in conjunction with mitosis, "mitosis" is often used interchangeably with "mitotic phase". However, there are many cells where mitosis and cytokinesis occur separately, forming single cells with multiple nuclei. This occurs most notably among the fungi and slime moulds, but is found in various different groups. Even in animals, cytokinesis and mitosis may occur independently, for instance during certain stages of fruit fly embryonic development.\n\nTranscription is generally believed to cease during mitosis, but epigenetic mechanisms such as bookmarking function during this stage of the cell cycle to ensure that the "memory" of which genes were active prior to entry into mitosis are transmitted to the daughter cells.click here:http://en.wikipedia.org/wiki/Mitosis#Overview
711105
The cell doesn't think.  It merely reacts to chemical signals that it detects.  The same goes for protozoa.  I strongly doubt that ants and worms do also.  I doubt that there's enough nervous tissue to form an actual thought.  They are certainly more complicated than protozoa, but they work on instinct, not by making conscious decisions.\n\nThe lesson that you were taught in your high school biology class was an analogy, not the literal truth.  The cell nucleus does control what happens in the cell, but it doesn't think.  It merely contains the programs that operate the cell, in the form of DNA.
759610
Mitosis:\n\nOccurs during cell division of somatic cells\n\nA full set of chromosomes is passed on to each daughter cell. This s the diploid number of chromosomess\n\nthe choromosomes and genes in each daughter cell are identical.\n\nIf new organisms are produced by mitosis is asexual reproduction they will all resemble each other and their parents. they are said to form a 'clone'.\n\n\nMeiosis;\n\nOccurs in the final stages of cell division leading to production of gametes.\n\nOnly half the chromosomes are passed on to the daughter cells, i.e. the haploid number of chromosomes.\n\nThe homologous chromosomes and their genes are radomly assorted between the gametes.\n\nNew organisms produced by meiosis in sexual reproduction will show variations from each other and form their own parents.