mitosis+or+meiosis

Arianna Gonzalez 
 * Students know how random chromosome segregation explains the probability that a particular allele will be in a gamete.**



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In [|biology], **meiosis** (pronounced [|maɪˈoʊsɨs] ([|help]·)  ) is a process of reductional division in which the number of chromosomes per cell is cut in half. In animals, meiosis always results in the formation of [|gametes], while in other organisms it can give rise to [|spores]. As with [|mitosis], before meiosis begins, the DNA in the original cell is replicated during [|S-phase] of the cell cycle. Two cell divisions separate the replicated chromosomes into four [|haploid] gametes or spores. Meiosis is essential for [|sexual reproduction] and therefore occurs in all [|eukaryotes] (including single-celled organisms) that reproduce sexually. A few eukaryotes, notably the [|Bdelloid] [|rotifers], have lost the ability to carry out meiosis and have acquired the ability to reproduce by [|parthenogenesis]. Meiosis does not occur in [|archaea] or [|bacteria], which reproduce via asexual processes such as[|binary fission]. During meiosis, the [|genome] of a [|diploid] [|germ cell], which is composed of long segments of [|DNA] packaged into [|chromosomes], undergoes DNA replication followed by two rounds of division, resulting in four [|haploid] cells. Each of these cells contains one complete set of [|chromosomes], or half of the genetic content of the original cell. If meiosis produces gametes, these cells must fuse during[|fertilization] to create a new diploid cell, or [|zygote] before any new growth can occur. 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 [|homologous recombination] during meiosis, each gamete, and thus each zygote, will have a unique genetic //blueprint// encoded in its DNA. Together, meiosis and fertilization constitute sexuality in the eukaryotes, and generate genetically distinct individuals in populations. In all plants, and in many protists, meiosis results in the formation of haploid cells that can divide vegetatively without undergoing fertilization, referred to as spores. In these groups, gametes are produced by mitosis. Meiosis uses many of the same biochemical 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].

In [|biology], **meiosis** (pronounced [|maɪˈoʊsɨs] ([|help]·)  ) is a process of reductional division in which the number of chromosomes per cell is cut in half. In animals, meiosis always results in the formation of [|gametes], while in other organisms it can give rise to [|spores]. As with [|mitosis], before meiosis begins, the DNA in the original cell is replicated during [|S-phase] of the cell cycle. Two cell divisions separate the replicated chromosomes into four [|haploid] gametes or spores. Meiosis is essential for [|sexual reproduction] and therefore occurs in all [|eukaryotes] (including single-celled organisms) that reproduce sexually. A few eukaryotes, notably the [|Bdelloid] [|rotifers], have lost the ability to carry out meiosis and have acquired the ability to reproduce by [|parthenogenesis]. Meiosis does not occur in [|archaea] or [|bacteria], which reproduce via asexual processes such as[|binary fission]. During meiosis, the [|genome] of a [|diploid] [|germ cell], which is composed of long segments of [|DNA] packaged into [|chromosomes], undergoes DNA replication followed by two rounds of division, resulting in four [|haploid] cells. Each of these cells contains one complete set of [|chromosomes], or half of the genetic content of the original cell. If meiosis produces gametes, these cells must fuse during[|fertilization] to create a new diploid cell, or [|zygote] before any new growth can occur. 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 [|homologous recombination] during meiosis, each gamete, and thus each zygote, will have a unique genetic //blueprint// encoded in its DNA. Together, meiosis and fertilization constitute sexuality in the eukaryotes, and generate genetically distinct individuals in populations. In all plants, and in many protists, meiosis results in the formation of haploid cells that can divide vegetatively without undergoing fertilization, referred to as spores. In these groups, gametes are produced by mitosis. Meiosis uses many of the same biochemical 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].