what is the biology term chiasmata?
400833
A chiasma, related to the Greek letter "X", is the technical term for the point where two chromatids are intertwined (interwoven) in a cell. The chiasmata are thought to be the points where two nonsister chromatids exchange genetic material during chromosomal crossover during meiosis (sister chromatids also form chiasmata between each other, but because their genetic material is identical, it doesn't cause any change in the resulting daughter cells). The chiasmata become visible during the diplonema stage of meiosis, but the actual "crossing-over" of genetic material is thought to occur during the previous pachytene Stage. When tetrads, which are composed of two pairs of sister chromatids, begin to split the only points of contact are at the chiasmata.
406009
This is a description of a process called "crossing-over" which takes place during Meiosis. More specifically metaphase I of Meiosis.\n\nYour answer is A) Meiosis
684084
the condition is termed chimerism. within an individual, a single nucleus or the nuclei of certain tissues can be polyploid while the others are diploid. an organism that contains tissues with different states of ploidy is referred to as a cytochimera.\n\ntetragametic chimerism is a less common cause of congenital chimerism. it occurs through the fertilization of two ova by two spermatozoa, followed by the fusion of the zygotes and the development of an organism with intermingled cell lines. this happens at a very early stage of development, such as that of the blastocyst. such an organism is called a tetragametic chimera as it is formed from four gametes - two eggs and two sperm.\n\nas the organism develops, the resulting chimera can come to possess organs that have different sets of chromosomes. for example, the chimera may have a liver composed of cells with one set of chromosomes and have a kidney composed of cells with a second set of chromosomes. this has occurred in humans, though it is considered extremely rare.\n\nit is also possible that the resulting organism, or the chimera, contains tissues with different states of ploidy such as the case you mentioned wherein a single nucleus or the nuclei of certain tissues can be polyploid while the others are diploid.
287246
meiosis (mīŏ'sĭs) , process of nuclear division in a living cell by which the number of chromosomes is reduced to half the original number. Meiosis occurs only in the process of gametogenesis, i.e., when the gametes, or sex cells (ovum and sperm), are being formed. Because fertilization consists of the fusion of two separate nuclei, one from each of the sex cells, meiosis is necessary to prevent the doubling of the chromosome number in each successive generation. An ordinary body cell is diploid; i.e., it contains two of each type of chromosome. The members of each pair are known as homologous chromosomes. An ovum or sperm is haploid; i.e., it contains only a single chromosome of each type and, therefore, half the number of chromosomes of the diploid cell. When the two haploid cells fuse, the diploid number is restored, and the plant or animal growing from the fertilized egg (zygote) has the usual diploid number of chromosomes in its cells. Just before meiosis each chromosome replicates to form two identical copies in the form of strands called chromatids joined together at a point called the centromere. In the first stage of meiosis, called the reduction division, the members of each pair of homologous chromosomes lie side by side and crossing over occurs. Each member of the pair then moves away from the other toward opposite ends of the dividing cell, and two nuclei, each with the haploid number of double-stringed chromosomes, are formed. Thus at the beginning of the second meiotic sequence, called the equational division, each cell nucleus contains one chromosome from each homologous pair and each chromosome is of two strands that are identical (except where crossing over has occurred). Then the chromosomes separate into their single strands which move toward opposite ends of the dividing nucleus. The result of meiotic division is four cells, each haploid, with one chromosome of each pair.
334948
Meiosis is also known as reduction division.\nIt is a type of nuclear division that gives rise to four reproductive cells (gametes) each with half the chromosome number of the parent cell. Two consecutive divisions occur. In the first, homologous chromosomes become paired and may exchange genetic material before moving away from each other into separate daughter nuclei. This is the actual reduction division because each of the two nuclei formed contains only half of the original chromosomes. The daughter nuclei then divide by mitosis and four haploid cells are produced. Four stages, prophase, metaphase, anaphase and telophase\n\nMitosis is a type of nuclear division that results in two daughter cells each having a nucleus containing the same number and kind of chromosomes as the mother cell. each chromosome divides lengthwise into two chromatids, which seperate and form the chromosomes of the resulting daughter nuclei. Four stages as well prophase, metaphase, anaphase and telophase, which merge into each other. Mitotic divisions ensure that all cells of an individual are genetically identical to each other and to the original gertilized egg.
973149
Asexual reproduction  as opposed to the sexual reproduction you and I know..  Usually happens in bacteria through a process known as binary fission.
1059733
http://en.wikipedia.org/wiki/Chimerism
258433
mitosis is asexual reproduction, cells divide and reproduce replicating their own DNA exactly\n\nmeiosis is sexual reproduction, new cells contain only half of their original DNA, and half from a different parent source
811865
flowering plants! we just learned this in my biology 110 class at penn state! oh, my professor would be so  proud :)
394770
The beginning of somatic cell division or mitosis is called prophase. In early prophase, the centrosomes move toward opposite poles of the cell, organizing the spindle microtubules between them. The sister chromatids become visible in the nucleus as they condense.In late prophase, the nuclear membrane breaks down and some of the spindle microtubules attach to the sister chromatids. The microtubules pull the chromatid pairs to the midline of the cell, or metaphase plate.The chromatids remain lined up between the poles of the cell during metaphase.Anaphase begins when the pairs of sister chromatids separate. The separated chromatids are now called chromosomes, and move toward the poles of the cell.The chromosomes arrive at the poles in telophase, and new nuclear membranes form around them.Division of the cytoplasmic components is called cytokinesis.In animal cells, cytokinesis occurs when a ring of actin and myosin filaments constricts the plasma membrane at the equator. Eventually, the parent cell is divided into two cells.Meiosis I-Prophase I-In the leptotene stage, the cell's genetic material, which is normally in a loosely arranged pile known as chromatin, condenses into visible threadlike structures. Along the thread, centromeres are visible as small beads of tightly coiled chromatin. Recall that centromeres are connection sites between sister chromatids, which are not yet distinguishable. As the chromatin becomes progressively ordered and visible, homologous chromosomes find each other and bind together. In this process, called synapsis, a protein structure called the synaptonemal complex attaches the homologous chromosomes tightly together all along their lengths.The zygotene stage sees the completion of synapsis. The paired homologous chromosomes are said to be bivalent. They may also be referred to as a tetrad, a reference to the four sister chromatids. During this stage, one percent of DNA that wasn't replicated during S phase is replicated. The significance of this cleanup act is unclear.The pachytene stage heralds crossing over. Nonsister chromatids of homologous chromosomes exchange segments of genetic information. Because the chromosomes cannot be distinguished in the synaptonemal complex, the actual act of crossing over is not perceivable through the microscope.During the diplotene stage, the synaptonemal complex degrades. Homologous chromosomes fall apart and begin to repel each other. The chromosomes themselves uncoil a bit, allowing some transcription of DNA. They are held together by virtue of recombination nodules, betraying the sites of previous crossing over, the chiasmata.Chromosomes recondense during the diakinesis stage. Sites of crossing over entangle together, effectively overlapping, making chiasmata clearly visible. In general, every chromosome will have crossed over at least once. The nucleoli disappears and the nuclear membrane disintegrates into vesicles.During these stages, centrioles are migrating to the two poles of the cell. These centrioles, which were duplicated during interphase, function as microtubule coordinating centers. Centrioles sprout microtubules, essentially cellular ropes and poles, during crossing over. They invade the nuclear membrane after it disintegrates, attaching to the chromosomes at the kinetochore. The kinetochore functions as a motor, pulling the chromosome along the attached microtubule toward the originating centriole, like a train on a track. There are two kinetochores on each tetrad, one for each centrosome. Prophase I is the longest phase in meiosis.Microtubules that attach to the kinetochores are known as kinetochore microtubules. Other microtubules will interact with microtubules from the opposite centriole. These are called nonkinetochore microtubules.Metaphase I-As kinetochore microtubules from both centrioles attach to their respective kinetochores, the homologous chromosomes align equidistant above and below an imaginary equatorial plane, due to cont
548454
Microchimerism\n\nIn Greek mythology, a chimera is a fire-breathing monster with the head of a lion, the body of a goat, and the tail of a serpent. In biology, a chimera is an organism consisting of tissues whose cells derive from two or more genetic sources. An apple tree, for example, can include grafts that enable it to produce a variety of apple types. In humans, such genetic mosaics reflect specific, intimate circumstances. The phenomenon is termed microchimerism because a one-cell population is typically much smaller than the other.\n\nAn organ transplant is an unnatural procedure that suddenly deposits many cells from one individual into another whose own organ has failed. It is similar to grafting in plants, and in fact, if the donor tissue reacts against the recipient's body, the condition is termed "graft-versus-host disease" (GVHD). When a transplant works, a peaceful co-existence evolves as recipient cells infiltrate graft tissue, and perhaps also as the transplanted cells alter their gene expression to modify their cell surfaces so that they are less likely to provoke the recipient's immune system. Microchimerism in transplant medicine does not refer to the transplanted material, but to small numbers of donor cells found outside the region of the transplant. For example, following transplantation of a liver, lymphoid and dendritic cells of the immune system often turn up outside of the liver, but with cell surfaces that match those of the donor, not the recipient.
284314
YES, as I was surprised to learn, the person is called a "chimera"...it's a REAL medical condition!\n\nshort, but informative article:\nhttp://www.thetech.org/genetics/ask.php?id=23
362010
Chromatin\nnoun\n\nsubstance forming chromosomes: the substance that forms chromosomes and contains DNA, RNA, and various proteins \n\nMicrosoft® Encarta® Reference Library 2004. © 1993-2003 Microsoft Corporation. All rights reserved.\n\nChromonema\n(plural Chromonemata)\nnoun\n\nchromatid core: the coiled central filament that forms the core of a chromosome strand (chromatid)\n\nMicrosoft® Encarta® Reference Library 2004. © 1993-2003 Microsoft Corporation. All rights reserved.
460864
The Flower:\nThe flower is the reproductive unit of some plants (angiosperms). Parts of the flower include petals, sepals, one or more carpels (the female reproductive organs), and stamens (the male reproductive organs). \nThe Female Reproductive Organs:\nThe pistil is the collective term for the carpel(s). Each carpel includes an ovary (where the ovules are produced; ovules are the female reproductive cells, the eggs), a style (a tube on top of the ovary), and a stigma (which receives the pollen during fertilization). \n\nThe Male Reproductive Organs:\nStamens are the male reproductive parts of flowers. A stamen consists of an anther (which produces pollen) and a filament. The pollen consists of the male reproductive cells; they fertilize ovules. \n\nFertilization:\nPollen must fertilize an ovule to produce a viable seed. This process is called pollination, and is often aided by animals like bees, which fly from flower to flower collecting sweet nectar. As they visit flowers, they spread pollen around, depositing it on some stigmas. After a male's pollen grains have landed on the stigma during fertilization, pollen tubes develop within the style, burrowing down to the ovary, where the sperm fertilizes an ovum (an egg cell), in the ovule. After fertilization, the ovule develops into a seed in the ovary. \n\nTypes of Flowers:\nSome flowers (called perfect flowers) have both male and female reproductive organs; some flowers (called imperfect flowers) have only male reproductive organs or only female reproductive organs. Some plants have both male and female flowers, while other have males on one plant and females on another. Complete flowers have stamens, a pistil, petals, and sepals. Incomplete flowers lack one of these parts. \n\nto find an extensive biology of plants please visit:\nhttp://users.pandora.be/educypedia/education/plantbiology.htm
226213
A Chimera (or chimeric protein) is a human-engineered protein or more specifically an enzyme with the catalytic activity that is encoded by a nucleotide sequence made by a splicing together of two or more complete or partial genes.
1180475
Tetraploid. (Probably a plant)
284810
Division Anthophyta (also known as angiosperms)