Cellular Multiplication

Discussion in 'Biology & Genetics' started by Present, Dec 12, 2005.

  1. Present BAMF Registered Senior Member

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    one thing that was never taught to me in biology class is how mutated cells can cause a full genetic change in a creature

    i understand ways that a mutation can occur but i dont understand how one different gene can change the physical structure of an animal.
     
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  3. Enigma'07 Who turned out the lights?!?! Registered Senior Member

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    you have an example?
     
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  5. Present BAMF Registered Senior Member

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    natural selection, some animals develope gene mutations which allow them to become dominant. i was wondering how a gene mutation translated into the change of the animals entire physical structure.

    is it that the animal developes the gene when its in the womb or something?

    am i confusing the words gene and cell
     
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  7. Enigma'07 Who turned out the lights?!?! Registered Senior Member

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    genes make protiens, a change in the gene will therfore cause a change in the protien which can cause change in appearance. Mutations generaly occur in the replication of DNA, so the offspring is the one effected. If a body (somatic) cell were to get a mutation, it would reproduce uncontrolably (basicaly become cancerous)
     
  8. Present BAMF Registered Senior Member

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    ok so the offspring of an animal whos cell was mutated are the ones that are different from the rest.

    ok i get it, thank you
     
  9. Buckaroo Banzai Mentat Registered Senior Member

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    That's it that Enigma said, if a cell of someone's skin or lung mutates, it either is neutral or something like a cancer, but the mutation won't spread all over the rest of the body of the person.

    A mutant individual arises when the mutation occurred in one of the germ cells of the individual's parents that joined to form the zygote.

    Then the individual from its first cell is a mutant; so all the other cells that duplicate from the zygote will inherit the mutated gene, making an individual that has all its cells with a different gene.

    The mutated gene is like a subtle (not necessarily) alteration in the "recipe" of the organism's growth.
     
  10. TheAlphaWolf Registered Senior Member

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    not necessarily... and the current thinking is that quite a few mutations are needed for a cell to become cancerous, and that's why the chances of you getting cancer increase as you get older- because you've had more mutations, and the chances of the right mutations happening increase as more mutations are added on.

    but yeah... nitpicking again.
     
  11. valich Registered Senior Member

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    Do you understand the differnce between genotype and phenotype? I'm not trying to be sarcastic or anything like that, but unless you know these two differences, I don't think you could understand any explanation?

    A gene is normally composed of two alleles. When one of those alleles mutates it changes the genotype. If that allele is dominant than it changes the phenotype
    (the physical expression of the genotype).
     
  12. Kumar Registered Senior Member

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    Can a possibilty exist that cancer mutations in genes be reversed or cancer cells start poducing specific antigens unabling immune system to hanle them? I mean can there be a possibilty that cancer is cured without modern medications surgery, chemo or radiation?
     
  13. TheAlphaWolf Registered Senior Member

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    I guess since you quoted me I'm supposed to reply... so I'll get to the point.

    Beats me.

    lol...If it's possible, it's probably not very practical though. There are probably hundreds (i'm just guessing here) of genes, and thousands of possible mutations a gene could have that make it an oncogene (cancer causing gene) Even if you could create an enzyme that recognized specific mutations, you would need a cocktail of hundreds of enzymes injected into the patient so that hopefully one of those types of enzyme could fix the problem...
    as for cancer cells producing antigens... I believe they do that already... you only get cancer when your immune system can't keep up with the cancer.

    and sure there's a possibility that cancer is cured without modern medications, surgery, chemo, or radiation... why don't you think of one?

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  14. valich Registered Senior Member

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    Special genes, called oncogenes, stimulate the production of growth-stimulating chemicals that trigger cell division. If an oncogene is irreversibly switched on, it can cause uncontrolled cell division and lead to the formation of a cancer. It is generally thought to be an irreversible process, that's why the cure is to kill or excise these cells (tumors) before they spread throughout the body (metastasize).

    Lot's of research is focussed on trying to identify cancer cells before they mutate and are able to start multiplying, but there are also many new techniques being explored in gene therapy:

    "Gene therapy is treating cancer by:
    - Blocking abnormal genes in cancer cells.
    - Repairing or replacing abnormal genes in cancer cells.
    - Encouraging even more genes to become abnormal in cancer cells so that they die or become sensitive to treatment.
    - Using viruses to carry treatment-activating enzymes into the cancer cells. The cancer cells would then either return to behaving normally, or die off because of other damage in the cell.

    The genes that are damaged may be:
    - Genes that encourage the cell to multiply or 'oncogenes'
    - Genes that stop the cell multiplying or 'tumour suppressor genes'
    - Genes that repair other damaged genes

    Gene therapy and oncogenes:
    Instead of trying to repair damaged oncogenes, scientists are trying to find drugs that can block the proteins that the oncogenes keep on making. They think this may be easier than trying true gene therapy and replacing the damaged oncogenes. But the body's cells make hundreds of different proteins that are all very similar. The difficulty is in finding a drug that will not block normal proteins and so have toxic side effects. Laboratory work is going on and these treatments may start to become available in the next few years.

    Gene therapy and TS genes:
    The tumour suppressor gene p53 is damaged in most human cancers. A lot of work has been going on into how to replace the damaged p53 gene with a normal one. But the scientists have to find a way to do this. Viruses have been used in the laboratory to carry the new gene into the cancer cells. If used in people, these carrier viruses are weakened so they cannot multiply and cause disease. But weakened viruses might be killed by the immune system before they had a chance to carry the new gene to the cancer cells. Some of the research work that has needed to be done has been to try to find a balance between.

    Stopping the carrier virus causing disease:
    Making sure the carrier virus is strong enough to get past the immune system without being killed. Early clinical trials are now in progress looking at treating cancers with modified p53-producing viruses. These trials are still investigating the technical side of developing the treatment - using the carrier virus to get the genes into cells for example. These are early days and this is a long process, unfortunately.

    Gene therapy and 'repair' genes:
    Gene therapy could be used to replace the damaged DNA repairing genes. But another approach, once these genes have been identified, is to damage even more of them. Even a cancer cell dies if it has too many mutations to its DNA. And if its repair genes are all damaged then it will carry on mutating until it dies. Or becomes more easily killed by other cancer treatments such as radiotherapy or chemotherapy. Laboratory work in going on, but clinical trials are still a little way off.

    VDEPT:
    This type of treatment is becoming more common, although it is still only given within clinical trials. It stands for 'Virus Directed Enzyme Prodrug Therapy'. A modified (harmless) virus is used to carry an enzyme into the cancer cells. Once the enzyme has found its way to the cancer cells, an inactive form of a chemotherapy drug, called a 'prodrug', is given to the patient. When the inactive prodrug reaches the cancer cells, the enzyme converts the prodrug into the active chemotherapy drug, so that it can kill the cancer cell. The idea behind this type of treatment is that it is targeted only to cancer cells. These are the only cells in the body that have the enzyme capable of converting the prodrug. As normal body cells should not be affected, there should not be too many side effects with this treatment. How effective this treatment is and whether there are side effects is being tested in the clinical trials that are now in progress in the UK and abroad.

    Tackling immortality:
    Scientists now know how cancer cells stay immortal. They have found the enzyme the cells use. If they can block or destroy the enzyme, then the cancer cells will age and die off as normal cells do after they have doubled 60 or so times.

    Tackling the cancer's blood supply:
    Cancers encourage the growth of new blood vessels to bring them oxygen and food. This is called 'angiogenesis'. Drugs that stop angiogenesis called antiangiogenics are being developed.

    Tackling cancer spread:
    Cancer cells do not stick together as well as normal cells. The proteins that normal cells use to stick to one another are often missing in cancer cells. If these could be restored somehow, then the cancer may not be able to spread. If normal cells become unattached and float free, they tend to die off quite quickly. Scientists think an oncogene is responsible for telling the cells they are attached when they are not. If this gene could be repaired using gene therapy, or the protein it makes blocked by a drug, then free floating cancer cells would die. The cancer cells would not be able to spread away from the primary tumour.
    Source: "Gene Therapy," Cancer Research UK, 04 March 2005.http://www.cancerhelp.org.uk/help/default.asp?page=131


    Also, new recent research has found a protein that may be able to prevent the replication of cancerous cells, but this is just a very preliminary finding and much more research and study needs to be done:

    "An ancient protein could be critical to stopping the uncontrolled division of tumor cells that cause cancer. Molecular Biology and Microbiology professor Mark Muller has found that the protein, called MKRN1, promotes the destruction of an enzyme called telomerase that enables rapid duplication of cells. While researchers have known for years that healthy cells repress telomerase, they haven't understood why...."To the best of my knowledge, this is the first example of how the enzyme (telomerase) itself can be turned off," Johnson said.

    The work focuses on the role that a long stretch of repeated DNA known as a telomere has in influencing cell length and, in turn, its lifespan. Each of the human's 46 chromosomes is capped on either end by telomeres, which help protect the cells. Each time a cell divides, the telomeres are shortened until eventually they become so small that the cell stops multiplying. Eventually the cell is eliminated from the body.

    When telomere ends do not shorten, division continues unabated. The body contains other mechanisms that kick in to stop the errant reproduction unless the telomerase enzyme is present. In laboratory tests, the MKRN1 protein has eliminated the presence of telomerase in tumor cells, said Muller, who conducted genetic research at The Ohio Sate University for 25 years before joining UCF last summer. Muller said that the MKRN1 gene is incredibly ancient and has likely been part of a human genetic makeup since the beginning of time. "Many different species have these genes, which emphasizes important collective roles in life" Muller said. "Moreover, mutating or altering the MKRN1 gene is lethal, thus, cells cannot live without these genes, further supporting a key role in growth control and cancer."

    Source: "Protein MKRN1 could stop replication of cancer cells," Cancer/Oncology News, 20 Apr 2005. http://www.medicalnewstoday.com/medicalnews.php?newsid=23103
     
  15. c7ityi_ Registered Senior Member

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    I have a question: what makes cells divide?
     
  16. spuriousmonkey Banned Banned

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    Depends on the situation and which cell we are talking about.

    In one situation cells proliferate under the influence of growth factors in a local situation. The cell needs to have receptors for a particular growth factor and this growth factor needs to be produced by itself or surrounding cells.
     
  17. valich Registered Senior Member

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    Plants and animals, or archaebacteria, bacteria, prokaryotes, and eukaryotes have different modes and phases of cell division - mitosis, meiosis, mitotic cell cycle, cytokininesis - but that doesn't really answer the question.

    Interphase is a growth stage where the cell increases its cytoplasmic volume and size in order to divide. So, in a sense, you can say that as cells enlarge, they eventually divide. But I am not comfortable answer this question in this way.

    "What Makes Cells Divide?
    Growth factors in the blood or produced by cells stimulate cells to divide. Certain genes in the cell then turn the cell "on" so that division can happen. After the cell has divided, other genes turn the cell "off" again.

    The chain of events is as follows:

    1) Growth factors attach to the cell membrane. They turn "on" messenger substances within the cell.

    2) The messengers send signals to the nucleus of the cell.

    3) Genes in the nucleus turn "on" the division process.

    4) The DNA in the nucleus replicates (doubles).

    5) The cell divides.

    6) Genes in the nucleus turn the cell "off."

    Changes (mutations) in the genes can affect their ability to turn the cells "on" or "off." This can cause uncontrolled cell growth and cancer."
    http://www.cdc.gov/excite/skincancer/mod02.htm
     
  18. Enigma'07 Who turned out the lights?!?! Registered Senior Member

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    or, more simply put, the divide when they get real big.
     
  19. valich Registered Senior Member

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    Not always. If that were true, then there would be no big single cell organisms that do not divide: evolution in action.
     
  20. shadowpuppet Registered Senior Member

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    From what i understand, the reasons for growth factors triggering mitosis remains a mystery, and one of the most widely researched ones as well.

    After all, if we figure out why cells multiply, then we could probably stop it, and things like, say, cancer, wouldn't be much of a problem anymore.
     
  21. Pete It's not rocket surgery Registered Senior Member

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    Are there any big single cells organisms that do not divide?
    If so, then how do they reproduce?
     
  22. Enigma'07 Who turned out the lights?!?! Registered Senior Member

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    the term "big" goes bact to the whole surface area vs volume thing
     
  23. valich Registered Senior Member

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    Most muscle cells do not divide, but when you exercise, muscle cells can get very big. You get bigger muscles, but the cells do not divide. Other stem cells can also get very large wiuthout dividing.

    In general, cell division occurs at the ratio of surface area of the cell to volume, and specialized cells are more apt through adaptation, genetics, and evolution to divide and share their function as needed keep the organism going.

    In general, biologically speaking:

    "Most proliferating cells in culture maintain a constant distribution of sizes and a constant average size, presumably by coordinating cell growth with progression through the cell division cycle. But it is far from clear how this coordination is orchestrated at the molecular level."

    Source: "Growing without a size checkpoint," by Jonathan B Weitzman, Journal of Biology, vol.2 (1):3, 2003. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=156594
     

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