Why is it that meiosis must occur to form egg and sperm cells?
831327
Because egg and sperm cells have only one set of chromosomes instead of two.  Most cells have a pair of each type of chromosome, plus two chromosomes which determine the gender of the individual.  Mitosis, the normal process of cell reproduction, results in two cells which each have two sets of chromosomes.  Meiosis results in cells having only one set of chromosomes.\n\nThe reason egg and sperm cells have only one set of chromsomes is simple... after sex, an egg is fertilized by combining with a single sperm cell.  Once the egg and sperm (each having one set of chromosomes) have combined, the fertilized egg has two sets of chromosomes - everything it needs to grow and live.
83115
It happens during meiosis, when the gametes are being formed. You know how chromosomes, in diploids, divide so that half of them go into one of the eggs/sperm and the other half go into the other, so that there's one of each in the gamete?\n\nWell, that is a way to re-combine the genetic material so that the offspring will have some from mom and some from dad. It's like having two sets of encyclopaediae, and combining them so that two new sets are produced, each with books from the two parents.\n\nNow imagine you have Volume 21 of the encyclopaedia from mom, and Vol. 21 from dad. You could assign one or the other to the new set being formed, but you want even more variety in the information.\n\nSo you take pages from one Volume 21 and _switch_ them with the equivalent pages from the other Volume 21.\n\nThat is crossing over and recombination. It increases the amount of possible children generated enormously.\n\nIt happens just before the chromosomes are segregated. In humans, we have 23 pairs of chromosomes. During meiosis, those 23 pairs split, forming 2 sets of 23 pairs each (chromatids). Those sets separate, and within each set the pairs recombine--that is, they cross over each other and exchange segments. Just like switching equivalent pages between the two same-numbered volumes of an encyclopaedia set.\n\nThat way the two sets of pairs, who will go on to form four new gametes, contain chromosomes that are neither identical to mom's nor to dad's, but a combination of segments of the chromosomes from both.
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Meiosis is the type of cell division by which germ cells (eggs and sperm) are produced. Meiosis involves a reduction in the amount of genetic material.\n\nMeiosis comprises two successive nuclear divisions with only one round of DNA replication.\nFour stages can be described for each nuclear division.
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(m)\n\nIn biology, meiosis is the process that transforms one diploid cell into four haploid cells in eukaryotes in order to redistribute the diploid's cell's genome.\n\nMeiosis forms the basis of sexual reproduction and can only occur in eukaryotes. In meiosis, the diploid cell's genome, which is composed of ordered structures of coiled DNA called chromosomes, is replicated once and separated twice, producing four haploid cells each containing half of the original cell's chromosomes. These resultant haploid cells will fertilize with other haploid cells of the opposite gender to form a diploid cell again. The cyclical process of separation by meiosis and genetic recombination through fertilization is called the life cycle. The result is that the offspring produced during germination after meiosis will have a slightly different blueprint which has instructions for the cells to work, contained in the DNA. This allows sexual reproduction to occur.\n\nMeiosis uses many biochemical processes that are similar to those used in mitosis in order to distribute chromosomes among the resulting cells; however the outcome is very different.\n\ngoto the following link for details about meiosis\nhttp://en.wikipedia.org/wiki/Meiosis
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Any mitotic division REQUIRES cytokinesis.  It's the split of the cytoplasm and it starts in telophase, the last part of mitosis.
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Mitosis ends with a complete copy of the DNA from the original cell to the new cell.  Meiosis results in a cell with only half of the DNA from the original cell.  The process involves the complete doubling of the DNA from the cell and 2 divisions, so that the cells have only half the chromosomes they need.  This cell is either the egg or the sperm depending on the sex of the animal it is in.  The cell generated from meiosis must combine with another cell from the opposite gender to create a viable embryo.
850288
in like every cell in your body ...without it you might not be alive...so remember it occurs in mostly well not even mostly...it occurs in every cell.i just learned about it in science...now we r moving onto genes ugh!!!btw just letting you know if you havent learned about mitosis at all and u are now...dont freak out cuz its hard cuz its not it easy to learn about!!
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First of all, gametes are produced only through meiosis and the location only occurs in the gonads(testes or ovaries). \n\nMitosis occurs all over the body for growth and repair while mitosis is for reproduction. Mitosis undergoes only one cell division to produce two identical daughter cells. Meiosis has 2 cell divisions producing 4 haploid daughter cells with mixed genes by synapsis and crossing over.
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Polar bodies form in meiosis, particularly during meiotic division of sex cells in females.
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Mitosis describes the process by which the nucleus of a cell divides to create two new nuclei, each containing an identical copy of DNA\nMeiosis, is the process by which certain sex cells are created. If you're male, your body uses meiosis to create sperm cells; if you're female, it uses meiosis to create egg cells
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It depends on the organism.  Humans are just built that way.  Other species like frogs continually generate oocytes (the egg precursor).  What happens in humans is usually not an absolute truth for other animals.  Some animals are asexual (no sperm needed).  All sorts of variations on the theme exists.
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two cell divisions.... one for meiosis 1 and one for meiosis 2
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Mitosis is the reproduction of body cells.  Meiosis is the reproduction of gamet of sex cells and only have 23 chromosomes in them.
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Mitosis and meiosis are sometimes called the two "nuclear division" processes
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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.
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The process of spermatogenesis involves multiple steps.\nwithin the wall of the seminiferous tubules, spermatigonium will split via mitosis. Each complete spermatogonium, aka primary spermatocyte will undergo meiosis. So one cell undergoes meiosis and produces 2 secondary spermatocytes. But the process is not yet comlete. These secondary spermatocytes must undergo a second meiotic division resulting in 4 spermatids which mature into sperm. \n\nSo for every starter cell, 4 sperms cells are formed at the end of this process.
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if you're a female human, you're born with all the eggs you'll ever have already made.\n\nthey arrest in meiosis ii, and as eggs mature, they complete meiosis. the longer they're arrested in that state (aka the older you are when the egg finally matures), the higher the chance that chromosome separation will not occur properly.