How does cell death contribute to development?
455723
controlled cell death (apoptosis) contributes to development in several ways. The two most common examples are as follows:\n\n1.  Look at your fingers and toes.  During the first stages of embryonic development of the hands, the entire hand is covered in a sheath of skin, like a webbed frog foot.  Apoptosis occurs to the "webbing", allowing you to have singled-out digits.  Sometimes, there is a genetic mutation that causes webbed toes, by mutating the gene that controls that particular type of apoptosis.\n\n2.  When your body is creating its network of blood vessels, the blood vessels start out as a solid cord of epithelium.  To make them hollow, the body uses apoptosis to get rid of the inner cells.\n\nOther examples include: deletion of the fallopian tubes in males, deletion of structures like a tadpoles tail as it becomes a mature adult, or simply controlling cell numbers, so that you do not end up with large cysts of skin or what have you.\n\nAlso, sorry about the lack of apostraphes, my computer is getting wonky suddenly.
355307
It isn't a very good control if your cells die before the experiment is complete.  More info is needed to get a more specific answer.
69908
Many (perhaps most) cells  stop growing when the reach confluence (this is called "Contact inhibition"). Generally, they do not die when they hit confluence, but certainly it will change the way they react to drug treatment and could be relevant.
531923
cells join to create tissues\ntissues join to create organs\norgans combine to create organ systems\norgan systems join to create organisms\n\ntheres two months of Biology for me, summed up right there
310214
That's a rather broad question...  You would probably have to specify it a little more to get the answer you are looking for.  But that said, there are numerous reasons as to why animal cells may develop an "abnormal" morphology.  Basically, there are perhaps two categories that can roughly be differentiated, even though - again - you have to be careful there.  One would be genetic reasons, another would be environmental reasons.  Genetic causes could be numerous as well, but take certain cancers for example, that have a genetic predisposition.  Certain environmental toxins can likewise lead to malformation of cells.  Please note that I was talking of a genetic "predisposition".  Often in case of cancer ebnvironmental and genetic effects are both responsible for the adverse effects observed.  So, the two categories are not ontological absolutes.  \n\nPerhaps what would help you to envision the problem is the basics.  First, cells divide mitotically in unicellular organisms.  consequently, a central question would be the default state of the cell.  There are three possibilities: (a) quiescence (i.e., the cell does not divide and needs an initiation of the mitotic process), (b) proliferation (i.e., cells default state is division and it needs particular factors to asure quiesence as needed in many multicellular organs), and (c) neither, since cell division is contextual.  The most common assumption in biology (and cancer biology, for that matter) is (a).  (b) has been suggested by  Carlos Sonnenschein and Ana Soto ("The Society of Cells. Cancer and Control of Cell Proliferation." New York: Springer, 1999).  Personally, I tend towards (c).  \n\nSecond, cells that proliferate during organogenesis have to further differentiate into the morphology and functionality they are to have in a specific organ.  \n\nThird, certain organs have cells that proliferate, whereas other organs don't.  Consequently, once everything goes well intially in organs of the second type, malformation may not occur as easily.  However, that said there are of course cancers of organs that normally do not have proliferating cells.  \n\nThese three basics may help you to ask your question a little more specifically and then seek out the literature that could give you answers accordingly.\n\nFinally, just remember that what is considered normal in science is the mean of a population.  But what determines this mean is often unclear.  I am thinking here for example of norms of reaction where cells may be shaped quite differently in response to environmental factors, and yet function wonderfully - in fact just exactly as they should given the particular environment.  Now, what is "deformed" would have to be probably understood functionally (i.e., a morphology associated with a functional break down).  And it seems to me that this is what you are looking for anyway.\n\nHope this helps.
829207
remember the phases in meiosis (in order) :Prophase, Metaphase, anaphase, telephase (pmat)\nMitosis\nI  INTRODUCTION \n\nMitosis, process in which a cell’s nucleus replicates and divides in preparation for division of the cell. Mitosis results in two cells that are genetically identical, a necessary condition for the normal functioning of virtually all cells. Mitosis is vital for growth; for repair and replacement of damaged or worn out cells; and for asexual reproduction, or reproduction without eggs and sperm.\n\nAll multicellular animals, plants, fungi, and protists, which begin life as single cells, carry out mitosis to develop into complex organisms containing billions of cells. Mitosis continues in full-grown organisms as a means of maintaining the organism—replacing dying skin cells, for example, or repairing damaged muscle cells. In the cells of the adult human body, mitosis occurs about 25 million times per second. Multicellular organisms such as sea stars, sea anemones, fungi, and certain plants rely on mitosis for asexual reproduction at particular stages in their life cycles, and mitosis is the sole mode of reproduction for many single-celled organisms.\n\nII  INTERPHASE \n\nThe life cycle of eukaryotic cells, or cells containing a nucleus, is a continuous process typically divided into three phases for ease of understanding: interphase, mitosis, and cytokinesis. Interphase includes three stages, referred to as G1, S and G2. In G1, a newly formed cell synthesizes materials needed for cell growth. In the S stage, deoxyribonucleic acid (DNA), the genetic material of the cell, is replicated. At this stage, DNA consists of long, thin strands called chromatin. As each strand is replicated, it is linked to its duplicate by a structure known as a centromere. When the S stage is complete, the cell enters a brief stage known as G2, when specialized enzymes correct any errors in the newly synthesized DNA, and proteins involved with the next phase, mitosis, are synthesized. \n\nIII  MITOSIS \n\nMitosis occurs in four steps. In prophase the replicated, linked DNA strands slowly wrap around proteins that in turn coil and condense into two short, thick, rodlike structures called chromatids, attached by the centromere. Two structures called centrioles, both located on one side of the nucleus, separate and move toward opposite poles of the cell. As the centrioles move apart, they begin to radiate thin, hollow, proteins called microtubules. The microtubules arrange themselves in the shape of a football, or spindle, that spans the cell, with the widest part at the center of the cell and the narrower ends at opposite poles. As the spindle forms, the nuclear membrane breaks down into tiny sacs or vesicles that are dispersed in the cytoplasm. Final disintegration of the membrane marks the beginning of metaphase. \n\nIn metaphase, the spindle fibers attach to the chromatids near the centromeres, and tug and push the chromatids so that they line up in the equatorial plane of the cell halfway between the poles. Like two individuals standing back to back at the equator, one chromatid faces one pole of the cell, and its linked partner faces the opposite pole. This precise orientation is necessary in order for the next step, anaphase, to occur. Anaphase begins when the centromeres split, separating the identical chromatids into single chromosomes, which then move along the spindle fibers to opposite poles of the cell. \n\nAs these two identical groups of single chromosomes gather at opposite poles of the cell, telophase begins. A new nuclear membrane forms around each new group of chromosomes. The spindle fibers break down and the newly formed chromosomes begin to unwind. If viewed under a light microscope, the chromosomes appear to fade away. They exist, however, in the form of chromatin, the extended, thin strands of DNA too fine to be seen except with electron microscopes. Mitosis accomplishes replication and division of the nucleus,
433277
A truly dangerous cancer cell has a number of characteristics- It undergoes uncontrolled division, it does not go through normal cell death (cellular suicide program-apoptosis), it is not constrained within it's normal biological area (e.g. a liver cancer cell will travel outside of the liver, while a normal liver cell will stay confined within the tissue).  So, any mutation that effects the cell suicide program, any mutation that changes the controls on cell division, and any mutation that causes the cell to travel outside the normal boundaries might be considered cancerous changes.
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Yeah, It is called oxidation. The cells die and the nuclei become dark, because of the toxic levels in oxygen. Funny how it keeps us alive.
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The importance of mitosis is the maintenance of the chromosomal set; each cell formed receives chromosomes that are alike in composition and equal in number to the chromosomes of the parent cell. Transcription 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\nMitosis is the process by which a cell separates its duplicated genome into two identical halves. It starts with 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. Mitosis 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.\nVR
780451
The cell cycle, or cell-division cycle (CDC), is the series of events in a eukaryotic cell between one cell division and the next. Thus, it is the process by which a single-cell fertilized egg develops into a mature organism and the process by which hair, skin, blood cells, and some internal organs are renewed. A specialized form of cell division is responsible for cellular differentiation during embryogenesis and morphogenesis, as well as for the maintenance of stem cells during adult life.\n\nThe cell cycle consists of four distinct phases: G1 phase, S phase, G2 phase (collectively known as interphase) and M phase. M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's chromosomes are divided between the two daughter cells, and cytokinesis, in which the cell's cytoplasm physically divides. Cells that have temporarily or reversibly stopped dividing are said to have entered a state of quiescence called G0 phase, while cells that have permanently stopped dividing due to age or accumulated DNA damage are said to be senescent. Some cell types in mature organisms, such as parenchymal cells of the liver and kidney, enter the G0 phase semi-permanently and can only be induced to begin dividing again under very specific circumstances; other types, such as epithelial cells, continue to divide throughout an organism's life.\n\nThe molecular events that control the cell cycle are ordered and directional; that is, each process occurs in a sequential fashion and it is impossible to "reverse" the cycle. There are two key classes of regulatory molecules that determine a cell's progress through the cell cycle: cyclins and cyclin-dependent kinases. Leland H. Hartwell, R. Timothy Hunt, and Paul M. Nurse won the 2001 Nobel Prize in Physiology or Medicine for their discovery of these central molecules in the regulation of the cell cycle.\n\nPhases of the cell cycle\n\n Schematic of the cell cycle. I=Interphase, M=Mitosis. The duration of mitosis in relation to the other phases has\nbeen exaggerated in this diagramAlthough the various stages of interphase are not usually morphologically distinguishable, each phase of the cell cycle has a distinct set of specialized biochemical processes that prepare the cell for entry into the next stage. It should be remembered that, throughout interphase, the cell carries out its normal metabolic activities and is actively engaging in transcription and translation of its genome.\n\nIn G1 phase, the cell carries on its usual metabolic activities while preparing to duplicate its DNA. These preparations often include growing by increasing the amount of cytoplasm and the number of important organelles such as mitochondria. (This is particularly important in organisms and cell types that divide their cytoplasm unevenly, as in budding yeast.) In G1 a diploid cell (such as a human cell) has a complement of 2N chromosomes, where N is the gene copy number; in sexually reproducing organisms this amounts to one chromosome inherited from each parent. The actual quantity of DNA is described as 2c, where the "c" value is measured in picograms and 1c is equal to the quantity of DNA in a single haploid genome. The end of G1 is demarcated by a "point of no return" beyond which the cell is committed to dividing; in yeast this is called START and in multicellular eukaryotes it is termed the restriction point. \nIn S phase, the cell duplicates its DNA. \nIn G2 phase, the cell continues with growth and metabolism in preparation for undergoing mitosis. In this quantity of DNA within the cell has increased to 4c, but the cell is still considered diploid. \nIn M phase the cell segregates its chromosomes so that both daughter cells receive a total complement of 2N. The four stages of mitosis - prophase, metaphase, anaphase, and telophase - also progress in a sequential and directional fashion, like the cell cycle as a whole. Telophase, the final stage of mi
779752
A living cell (like a cell from the liver, lungs, brain, etc...) will die soon after it was removed from its original "place" (liver, lungs, brain, etc.) as it has no more nutrients-supply (by blood venes, for example!) except it is kept in an artificial environment, a culture medium, which is suited to it's very specific needs.\n\nA living cell that is an organism needs a special suited environment, too (a diatom won't survive in the desert...). But it is not depending on an EXTERNAL supply of nutrients, as it "searches" its nutrients on its own. Bacteria, for example, don't need blood venes to grow in order to make cell division, they just need an environment which supplies all the needed nutrients. That's why bacteria can grow nearly everywhere, while lung cells  would die short after you dispersed them on an old dank sponge.\n\nHope I helped you. Excuse my English, please, it's not my first language. Good luck for tomorrow! ;-)
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a group of cells form a tissue
970697
All the answers are here --> http://en.wikipedia.org/wiki/Cell_%28biology%29\n(and in your book)
570228
There's also cell apoptosis.  infected cells put out a self-destruct signal so the virus can't reproduce.  its actually what i work on, with herpes
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They do in a developing embryo, but not in a fully developed animal/person.\n\nWhat brain cells CAN do is create connections between each other, creating more neural pathways that aid in recollection.  But if you damage your brain enough, it won't recover.
795038
Because mitosis is the process where cells divide to perform such activities like cell replacement and repair. Their environment is fairly stable and not dangerous/harmful so they rarely divide. So the damaged cells can stay that way for life due to the slow/non-existent division of mitosis.
512334
Genetics - each time the cells divide, telomeres are lost from the ends of the chromosomes and this leads to the cells aging and dying once too much information has been lost.