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Thursday, April 21, 2011

Telomeres and Spock


"my what lovely telomeres you have" said the wolf-virus
to the little red-riding hood-cell
 

  Cells have their own version of Spock's famous missive "Live long and prosper."  Cells make this statement using repetitive DNA sequences found on end of chromosomes called "telomeres." Telomeres act as a cap on the end of chromosomes.  They are thought to be another "guardian of the genome" of sorts.  Some scientists believe that longevity is related to telomere length. In fact, telomeres have been shown to be longer in individuals who are healthy and exercising compared to individuals who are under stress.



What's even more interesting is that telomeres are thrown out or lost during cell division so they have to be "remade" using a specific polymerase.



How do telomeres protect DNA?


What is the significance of telomeres being made from repetitive DNA? (what is repetitive DNA and what is it good for?).


What determines how long telomeres are?


How are telomeres related to cell function?


Some bacteria have telomeres,  so from one perspective it looks like they were handed down via evolution.  Why use what appear to be accidental sequences to make the ends of chromosomes? Is there some advantage or design feature inherent in these chromosomal pieces?

40 comments:

  1. looking it up right now wow there is allot in this one

    ReplyDelete
  2. How do telomeres protect DNA?

    “The DNA sequence in the telomere attracts proteins that form a protective cap around the fragile ends of the DNA strands.”

    http://nobelprize.org/nobel_prizes/medicine/laureates/2009/press.html


    What is the significance of telomeres being made from repetitive DNA? (What is repetitive DNA and what is it good for?)

    Repetitive DNA is DNA sequences that have many copies inside the genome. Repetitive DNA does not code for proteins. Some evolutionists say that repetitive DNA is an evolutionary device that promotes formation of new genes by suppressing gene conversion (which is one of the ways a gene can be mutated.)

    A journal article abstract I read said that repetitive DNA is essential to genome function in many ways. Repetitive DNA helps “to format expression of unique coding sequence files and to organize additional functions essential for genome replication and accurate transmission to progeny cells.” It is also “fundamental to the cooperative molecular interactions forming nucleoprotein complexes.” Repetitive DNA also “serve[s] either as initiators or boundaries for heterochromatin domains and provide[s] a significant fraction of scaffolding/matrix attachment regions (S/MARs).”

    http://www.ncbi.nlm.nih.gov/pubmed/15921050

    This last function of repetitive is describing telomeres. Maybe it is significant that telomeres are made from repetitive DNA since telomeres are so essential to cell function, organ function, and life in general. In the event of a telomere being damaged, the cell has many copies of the DNA that makes up telomeres. Perhaps this is the significance of telomeres being made from repetitive DNA


    How are telomeres related to cell function?

    Telomeres’ importance for cell function becomes evident when telomeres are damaged, or missing. An article from the journal “Nature” said this about telomeres:

    “Telomere loss and uncapping provokes progressive tissue atrophy, stem cell depletion, organ system failure and impaired tissue injury responses.”

    One main function of telomeres is to protect against cellular aging. Once the telomeres are compromised, the cell begins to age.

    http://www.nature.com/nature/journal/v469/n7328/full/nature09603.html

    One really interesting thing I found (from another journal article) was that the same telomere DNA is found in many different organisms—from plants to animals to man. An experiment was done in which telomere DNA from one organism was put into another different organism. The foreign telomere DNA worked perfectly well to protect the second organism as if it had originally been created there.

    http://nobelprize.org/nobel_prizes/medicine/laureates/2009/press.html

    ReplyDelete
  3. 1. The telomeres protect the DNA from deteriorating or getting fused with other parts of DNA. During replication, parts of the telomere are lost because they cannot be transcribed. They are necessary because without the telomere being lost, coding sections of DNA would be lost during replication. After replication, the telomere is replaced with the enzyme telomerase reverse transcriptase.
    2. The benefit of telomeres being made of repeating DNA is that when parts of it are lost during replication, identical portions of DNA are still present.
    3. Telomere length is controlled by enzymes associated with DNA replication. The telomeres are shortened when the lagging strand of the 5’ section of DNA is lost during replication, and they are lengthened by proteins such as telomerase reverse transcriptase.
    4. Telomeres are vital in the cell replication, and they serve as a buffer to degradation of DNA parts during replication. When the telomeres no longer present, the cell may become cancerous or stop the cell cycle.
    5. The sequences in telomeres at the end of chromosomes are advantageous because they don’t code for proteins and are degraded during replication. Since they are not necessary for coding proteins, they are well suited to be removed and replaced during the cell cycle.

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  4. It seems that from the research that I have found, that telomeres function in protecting chromosomes from unraveling, and also not from sticking to one another which allows them to be organized and also able to be copied. When a cell divides, the telomere becomes shorter thus also causing the cell to become aged. Thus, telomeres (or a lack of) must be one of the many markers that eventually lead to apoptosis. On the other hand, there is an enzyme that helps to prevent the cell from aging and the telomere from being shortened. It is called telomerase (which is kind of weird because usually things that have an -ase- at the end of it break down something). How does it do this? Well, from my source, "Telomerase extends telomere DNA, providing a platform that enables DNA polymerases to copy the entire length of the chromosome without missing the very end portion."

    It is interesting to know that most of our own cells do not divide very frequently and therefore do not lose their telomeres that fast. But on the other hand, cancer cells divide rapidly and seem to be able to maintain their telomeres. Some scientist say that they are able to maintain their telomeres because they can maintain a level of telomerase. So you would think that maybe taking out the telomerase would cause the cancer cell to not be as long-lived. Research is still being carried out on it.
    http://www.sciencedaily.com/releases/2009/10/091005110401.htm

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  5. 1. Telomeres protect the DNA by keeping it from deteriorating and fusing with other chromosomes.

    2. "DNA sequences that are repeated in the genome. These sequences do not code for protein." This repetitive DNA is useful in that it has "...repeated signals in the DNA are necessary to format expression of unique coding sequence files and to organise additional functions essential for genome replication and accurate transmission to progeny cells". It basically links strands of DNA together, making genes.
    http://www.medterms.com/script/main/art.asp?articlekey=5309

    3 and 4. I read that generally, telomeres are longer the younger you are. Also, since telomeres are involved in cell division and act as the "internal clock" in cells, each time the cell divides, it's telomeres shorten. Interestingly, cancer cells telomeres continue to grow after each division.

    5. It seems like a great idea to have telomeres on the ends of chromosomes to protect them from deteriorating. And since they also anchor chromosomes to the nuclear membrane, so they don't float away, as well as prevent clumping in anaphase, they have multiple advantages. I think this must show that there is a creator involved and that telomeres are no accident, because how long would it take for the cell to figure out that they could be so useful and to get all the pieces of the telomeres into the right place?

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  6. I was thinking that maybe the telomere's protect the DNA by keep it from unwrapping when it is in a chromosome and helping it keep it's shape so there will be no defects and the chromosome will be protected. When I looked it up I was somewhat correct. "A telomere is a region of repetitive DNA sequence at the end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes."

    If I remember correctly, repetitive DNA is used for rRNA so that the ribosome can be made. Maybe the significance of telomeres being made out of repetitive DNA is so that they will all have the same sequence and so that they can cap off the chromosome well during duplication.

    "The length of the telomere influences the stability of genetic information just interior of the telomere, since the nucleotide sequences at the ends of a chromosome are not copied by DNA polymerase. Successive copying can thus shorten telomeres, sometimes to the point that functional genes near the telomeres are lost, and this may play a role in cellular senescence and age-related diseases."

    What looks to be accidental sequences actually help the chromosomes a great deal. It protects the ends of the chromosomes from deterioration or from fusion with neighboring chromosomes." This is definitely advantageous and something that is this essential could not be accidental or random.

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  7. 1. Telomeres protect the DNA by preventing deterioration or fusion with neighboring chromosomes. They do this by allowing the shortening of chromosome ends which occurs during chromosome replication. They also serve a sort of “capping” function to keep chromosomes from sticking together.

    2. Repetitive DNA is noncoding DNA sequences within the genome. Strong evidence supports the conclusion that repetitive DNA is a tool used to catalyze the formation of new genes by suppressing gene conversion. However, within telomeres it is activated by the substance telomerase and causes repetitive DNA sequences to be added to the ends of the DNA. In this way the telomeres capping function is carried out.

    3. It is believed that there is a certain area on the chromosome that controls telomere length. Some scientist in the UK reported “We present preliminary analysis of a strong candidate gene in the region, the DNA helicase DDX11. In conclusion, we report mapping of the first locus that determines mean telomere length in humans (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1196417/).”

    4. Telomeres are a regulatory part of the cell. Not only do they protect the integrity of the cell by guarding against the wearing away or unraveling of DNA but they also regulated how many times a cell divides. Every time cell division occurs a certain portion of the telomere falls off. After a certain amount of divisions the telomere is depleted and the cell dies. This regulatory function may be connected to aging and cancer.

    5.One advantage to using these repetitive sequences could be the fact that part of the telomere drops off every time the cell divides. If the telomere were one long strand of specific coding DNA the telomere would change in function or die every time a piece of it was taken away. With repetitive sequences the telomere can lose parts of itself during cell division and still keep its structural integrity and function.

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  8. 1.They prevent Chromosomes from fusing with other chromosomes. Also, they provide protection for the fragile nucleic acids in the chromosomes.
    2. The benefit of having extra copies of DNA is that if any DNA did become damaged, it could be replaced. Also, this links specific DNA sequences together to create genes.
    3. The length of Telomeres are determined by specific enzymes. Also, there is an area on the chromosome that determines initial Telomere length. Basically, The length of Telomeres are determined by hereditary information yet they can fluctuate in size using enzymes.
    4. Telomeres are related to the cell cycle. The length of a telomere determines the number of times it can undergo the cell cycle. However, in cancerous cells, this factor is not present.
    5. Although Telomeres aren’t involved in protein manufacture, they do play an essential role in cell replication, and chromosome separation/protection.

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  9. 1.Telomeres protect DNA form unraveling. Loss of DNA capping by telomeres is also responsible for diseases that cause rapid aging. Older people also have shorter telomeres and loss of telomeres contribute to diseases that are seen in natural aging. Telomeres also allow cells to distinguish healthy chromosome ends from damaged DNA. This keeps a potentially lethal DNA damage response from occurring. DNA repairing can threaten chromosome ends and genome instability can arise. They also keep chromosome ends from deteriorating and fusing with neighboring chromosomes. During chromosomal replication, it causes the shortening of the chromosomal ends which deters the degradation of genes near the end of the chromosomes. Without telomeres cells would lose the ends of their chromosomes, including the information that they contain.
    2. Repetitive DNA plays a significant role in keeping the stability and structure of the chromosome. Evolutionists also believe that “repetitive DNA...catalyzes formation of new genes by suppressing gene conversion.” Gene conversion is what allows species to exist. Telomeres seem to be made of this repetitive DNA because it is constantly being remade. After cell division the telomeres are consumed, but they are then replenished by an enzyme after cell division is complete. It would make more sense for the telomeres sequence to always be the same then for a different sequence after every division is complete.
    3. Every time a cell divides telomeres become shorter. After multiple cell divisions the telomeres are so short the cell either dies or ends up in a resting stage. In a healthy cell the length of telomeres can show how many times a cell has divided.
    4. Telomeres are extremely important in cell division. Without telomeres important gene sequences would be last and chromosomes would not be replicated correctly. They also play a role in aging. Loss of DNA capping by telomeres is also responsible for diseases that cause rapid aging. Older people also have shorter telomeres and loss of telomeres contribute to diseases that are seen in natural aging. Telomeres keep the cell stable as well.
    5. DNA obviously needs a cap, for many reasons. From a completely evolutionist perspective it would make sense to cap DNA with this because it protects it in so many ways. Keeping it from unraveling being a big one. All of the above is evidence that there is advantageous design in these telomeres, without them our DNA would not work correctly or replicate correctly and we would not have the genes we need to survive.

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  10. 1. Telomeres allow cells to distinguish chromosome ends from broken DNA
    If DNA is broken there are two options after the cell cycle is stopped: Repair or Death. Repair can occur in two ways:
    Homologous Recombination (HR) -- Error-free but need homologue nearby
    Non-homologous end-joining (NHEJ) -- Error-prone but saves chromosome from degradation.
    Telomeres prevent chromosome fusions by NHEJ. Telomeres also provide a mechanism for "counting" cell divisions.

    2. Repetitive DNA refers to substrings of the genome that repeat multiple times. "Generic repeated signals in the DNA are necessary to format expression of unique coding sequence files and to organise additional functions essential for genome replication and accurate transmission to progeny cells. Repetitive DNA sequence elements are also fundamental to the cooperative molecular interactions forming nucleoprotein complexes. "

    3. "Telomere length varies greatly between species, from approximately 300 to 600 base pairs in yeast[8] to many kilobases in humans, and usually is composed of arrays of guanine-rich, six- to eight-base-pair-long repeats. Eukaryotic telomeres normally terminate with 3′ single-stranded-DNA overhang, which is essential for telomere maintenance and capping."

    4. "During cell division, enzymes that duplicate DNA cannot continue their duplication all the way to the end of the chromosome. If cells divided without telomeres, they would lose the ends of their chromosomes, and the necessary information they contain. The telomeres are disposable buffers blocking the ends of the chromosomes and are consumed during cell division and replenished by an enzyme, the telomerase reverse transcriptase."

    -Sarah Gonzales

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  11. 1)
    Telomeres protect both telomeric DNA and DNA in chromosomes by the formation of loops in the DNA and a complex of TRF1, TRF2, and TIN2 telomeric proteins that shield the DNA from nucleases.


    2)
    Repetitive DNA is DNA that does not code for proteins. According to an article by Department of Biochemistry and Molecular Biology at the University of Chicago, “Generic repeated signals in the DNA are necessary to format expression of unique coding sequence files and to organize additional functions essential for genome replication and accurate transmission to progeny cells. Repetitive DNA sequence elements are also fundamental to the cooperative molecular interactions forming nucleoprotein complexes...the repetitive component of the genome plays a major architectonic role in higher order physical structuring.”

    I think frendtem nailed the reason that telomeres are made from repetitive DNA. Like he said, “when parts of it are lost during replication, identical portions of DNA are still present.”


    3)
    In humans, length of telomeres is genetic, determined by a locus (a specific site on the chromosome). http://www.cell.com/AJHG/abstract/S0002-9297(07)62551-8

    Interestingly, in cancer patients “...telomerase and telomere length may be influenced by the degree of tumor cell content in tumor specimens.” The more cancer cells present, the more telomerase will add nucleotides to the telomeres, lengthening them. Basically, cancer can mean longer telomeres. http://clincancerres.aacrjournals.org/content/3/10/1849


    4)
    Telomeres are important for cell division since they help to ensure the proper division of DNA as well as protect the DNA from nucleases.


    5)
    The use of repeating sequences to form telomeres is advantageous and shows design: If a non-repeating sequence was used to form a telomere then any mutations in the sequence or loss of portions of the sequence would break down the telomere and the chromosomes would be damaged, divided incorrectly, etc. As Shannon said, “With repetitive sequences the telomere can lose parts of itself during cell division and still keep its structural integrity and function.”

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  12. Sam and Frendtem,

    Good points. Even if a small piece of Telomere sequence is left it might have the opportunity to for a template....might also be the reason that some repeat DNA is very short...i.e., repeats of three nucleotides. Very intereseting. Wonder if anyone else has thought of that or looked for the "template function." Dr Francis

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  13. How do telomeres protect DNA?
    this is what I got from an article online: "McClintock analyzed the consequences of chromosome breakage by constructing a maize strain in which dicentric chromosomes (those containing two centromeres) could be produced with high frequency. Dicentric chromosomes break when the two centromeres are drawn to opposite poles of the mitotic spindle during cell division. In her work with this maize strain, McClintock noted that the broken chromosomal ends were unstable, and that these ends fused with any other broken ends with which they came in contact. If the original chromosome reformed when such contact occurred, then the cycle of breakage and fusion could be repeated. This cycle was broken, however, when dicentric chromosomes were present in embryonic cells; in these cells, the broken ends were somehow "healed" (McClintock, 1941). Today, researchers know that the ends were healed by the addition of a telomere, a process that is catalyzed by an enzyme called telomerase. Telomerase is active in germ cells, embryonic cells, and some somatic cells, but not in the endosperm cells that McClintock examined (McKnight & Shippen, 2004).

    What is the significance of telomeres being made from repetitive DNA? (what is repetitive DNA and what is it good for) "We find that repetitive elements present at high frequency in mammalian telomeres, but rare in bacteria, down-regulate CpG-induced immune activation. Suppressive activity correlates with the ability of telomeric TTAGGG repeats to form G-tetrads." Repetitive DNA are "DNA sequences that are repeated in the genome. These sequences do not code for protein. One class termed highly repetitive DNA consists of short sequences, 5-100 nucleotides, repeated thousands of times in a single stretch and includes satellite DNA. Another class termed moderately repetitive DNA consists of longer sequences, about 150-300 nucleotides, dispersed evenly throughout the genome, and includes what are called Alu sequences and transposons."

    What determines how long telomeres are?
    "Research now shows that exercise has the power to turn back time. Exercise affects your telomeres, making them longer and stronger. The telomere is your biological clock. It determines how long you live. And how well you live.
    Telomeres are “caps” at the ends of every cell’s DNA. They act like the plastic fittings on the ends of your shoelaces, and keep your DNA strands from fraying." Exercise and living a "stress free" lifestyle will help the telomeres grow...probably the chemicals that are sent out from these things build up the telomeres. When we don't exercise or when we are stressed, these chemicals are probably not released, therefore the DNA is free to break up, causing you to age faster.

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  14. How do telomeres protect DNA?
    Telomeres are dispoable buffers blocking the ends of chromosomes and are consumed during cell division and replenished by an enzyme, the telomerase reverse transcriptase. Without telomeres, the ends of the chromosomes would degenerate causing damage to the genome.

    What is the significance of telomeres being made from repetitive DNA? (what is repetitive DNA and what is it good for?)
    Scientists think repetitive DNA catalyzes the formation of new genes by suppressing gene conversion. According to research, it can operate on genes within a multigene family or it can operate interchromosomally on gene homologues.
    I had a hard time finding the significance of temomeres being made of repetitive DNA, but my hypothesis is that since by being repetitive, it can also act as “backup” DNA.

    What determines how long telomeres are?
    Gene TERC determines how long telomeres are and how quickly they shorten. “Telomerase is a ribonucleoprotein polymerase that maintains telomere ends by addition of the telomere repeat TTAGGG. The enzyme consists of a protein component with reverse transcriptase activity, and an RNA component, encoded by this gene, that serves as a template for the telomere repeat.”

    http://www.genecards.org/cgi-bin/carddisp.pl?gene=TERC

    How are telomeres related to cell function?
    Telomeres have important roles in assuring that genetic material is divided equally when cells multiply, and it is thought that they may be involved in regulating cell division in human ageing and cancer.

    http://onlinelibrary.wiley.com/doi/10.1038/npg.els.0001168/abstract

    Some bacteria have telomeres, so from one perspective it looks like they were handed down via evolution. Why use what appear to be accidental sequences to make the ends of chromosomes? Is there some advantage or design feature inherent in these chromosomal pieces?
    Once again, I couldn’t find much research on this specifically. It could seem accidental, since the telomeres don’t code for any proteins. Because they don’t code for any proteins, they could be useful since they degrade anyway. I guess the fact that seeming “useless” DNA is actually vital to the cells function could point towards design.

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  15. Telomeres protect DNA in that when DNA replicates DNA polymerase only adds nucleotides to the 3 prime end so thus on the end, the 5 prime side, the nucleotides will be unable to be added. Telomeres account for this in that they are repetitive sequences which allow the DNA polymerase to finish off the replication. The repetitive DNA is probably used because it signifies that the DNA is there not to be transcribed and is not useful for proteins. Nonetheless there is still DNA that is lost even if it is unneeded sequences in telomeres. What determines how long telomeres are is how much is cut off each time the DNA replicates and also how much the telomerases put back on to the telomeres. Telomeres function in the cell in that they prevent chromosomes from being broke down and protecting them and they also prevent the chromosomes from bonding to each other. These sequences that seem random and are repetitive are perfect for their specific function. Because they are repetitive they keep the sign that they are noncoding and also as they are broken down during cell division it is easy to add the nucleotide sequence to the telomeres since it will be the same every time.

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  16. 1.Telomeres protect DNA from deteriorating or getting attached to other surrounding chromosomes.
    3."Human telomeres are approximately 10,000 base pairs long at birth. At around 100 years of age, that amount decreases to about 5,000 base pairs. Telomerase can reverse or stop the shortening process. It typically increases the length of telomeres during the formation of gametes for the purpose of ensuring that offspring inherit long young telomeres."
    http://www.examiner.com/health-and-science-in-hartford/telomeres-and-longevity-the-long-and-short-of-it

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  17. 1. Telomeres protect the chromosomes from losing important DNA sequences during replication. Since the proteins that are responsible for transcripting DNA into RNA cannot go to the very end of a crhomosome, telomeres cap the chromosomes and allow all of the DNA that codes for something to be copied. They also prevent the ends of chromosomes from sticking together.

    2. Repetitive sequences do not code for anything but can serve a purpose as a structural aid. Since the ends of a chromosome must be disposed of during replication, repetitive DNA would be good to have on the end since it does not code for anything and no genetic material would be lost. Repetitive DNA is also extremely useful as a DNA template. I took Dr. Francis’ big hint and looked into template DNA. It speeds up DNA replication significantly so if only a few nucleotides of the telomere are transcribed for the new chromosomes during DNA replication then a new telomere can for very quickly, ensuring that the new chromosomes are not able to stick to each other.
    3. I noticed a few people that commented before me mentioned that telomeres gradually shorten permanently with each cell division and when it is too short the cell either dies or ceases to replicate. Sam also mentioned that cancer patients have abnormally long telomeres. If their telomeres never shorten then cells never stop dividing so maybe there is a strong link between the two.
    4. As above mentioned, longer telomeres can mean faster cell division which is bad in the case of cancer patients but good for just about anything else. Fast cell turnover means a healthy metabolism, clear skin, strong immunity, and quick injury recovery.
    5. Telomeres are not accidental. Though they are repetitive and do not code for proteins and can technically be disposed of easier than coding DNA sequences, they are necessary for cell function. They even have their own enzymes, telomerase, that repair them. Telomeres are kind of like the timer for the cell. When they get too short, the cell’s time is up and it stops replicating. If a telomere is too short then that means that the cell is not healthy. So telomeres can be used as a signal for when something is wrong in the body or just simply tell the body when it’s time is up.

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  18. 1When DNA is broken there are two options after the cell cycle is stopped: Repair or Death. Therefore, telomeres prevent chromosome fusions by NHEJ, Non-homologous end-joining, which is error-prone but saves chromosome from degradation. And this fusion-bridge-breakage cycles leads to genomic instability which in turn can result in cell death or neoplastic transformation, so telomeres are specialized structures that essential for protecting chromosome ends and ensuring chromosome stability, and provide a mechanism for “counting” cell divisions.
    http://mcb.berkeley.edu/courses/mcb135k/telomeres.html

    2Repetitive DNA are DNA sequences that are repeated in the genome. These sequences do not code for protein, but serve either as initiators or boundaries for heterochromatin domains and provide a significant fraction of scaffolding/matrix attachment regions (S/MARs) suggests that the repetitive component of the genome plays a major architectonic role in higher order physical structuring.
    http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=297244

    3Irregularities in telomere length have been implicated in several types of diseases due to cel mutation that related to aging, such as cancer.

    4Oxidative stress, depression, chronic inflammation and psychological stress have been demonstrated to potentially affect telomere length.
    http://www.suite101.com/content/telomere-functions-in-human-diseases-and-cancers-a343811

    5The telomere is designed at the end of chromosome because telomeres are important in cell division that they "cap" the end-sequences and themselves to prevent from lost in the process of DNA replication.

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  19. (1) Telomeres stabilize and allow the complete replication of the ends of chromosomes. Chromosomes are stabilized by telomerase. Telomerase is a telomere enzyme which is known to be “a specialized DNA polymerase that adds telomeric sequences onto chromosome ends” (Greider). This addition of sequences balances the natural loss of repeats from chromosome ends. Also telomeres being also known as the special protective cap located at the end of the chromosome, it protects the genetic information stored in the chromosomes to be passed from parents to their children during mitosis.

    (2) Repetitive DNA is the substrings of the genome that repeat multiple times. The benefits of repetitive DNA according to Szostak and Blackburn, is that the telomere repetitive DNA sequence protects the chromosomes from degradation. Also the repetitive DNA sequence in the telomere attracts proteins that form the protective cap at the ends of the chromosomes.

    (3) According to Saladanha, “the total number of telomeric repeats at the terminal end of a chromosome determines the telomere length”. However only telomeric repeats bound by telomere binding proteins are stabilized. It is very important that the length of the telomere is stable in order to prevent the contribution to the proliferative capacity of many cancer cell types. Another factor that determines how long telomeres are, are telomere capping proteins, telomerase, and DNA replication enzymes.


    http://nobelprize.org/nobel_prizes/medicine/laureates/2009/press.html

    http://www.annualreviews.org/doi/pdf/10.1146/annurev.bi.65.070196.002005

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  20. Telomeres protect DNA by helping them not deteriorate and fuse with other parts of DNA. They help the chromosomes from unraveling so they can be organized and easily copied. The significance of telomeres being made from repetitive DNA is it helps if certain parts of DNA are lost they still have some identical portions of it. They have many sequences inside the genome. Some evolutionists believe that repetitive DNA can catalyze formation of new genes by suppressing gene conversion. Repetitive DNA helps keep stability and structure of the chromosomes, and acts as a DNA template. Telomeres lengths are determined by the cell division. The lengths can be determined by the several types of diseases also due to the cell mutation. Depending on how many times it can go through the cell cycle (division), a portion of the telomere falls off. This can cause the cell to become depleted and the cell dies, which is a function of cancer. Evolutionists believe that it can appear to be an accidental sequence to make the ends of chromosomes. But God has displayed his incredible work and design by allowing it protects them from deteriorating, not clumping or sticking together and many other characteristics that there is no way that this can be accidental.

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  21. 1) Telomeres protect DNA by making sure base pairs stay on the chromosome and defining the end of the chromosome. They show the cell that the end of the chromosome is ...well the end of the chromosome instead of broken DNA. That way, the cell doesn't try to repair the end of the chromosome when it doesn't need to be repaired.

    2) Repetitive DNA is DNA that repeats several nucleotides and doesn't code for protein. It is helpful that telomeres are made of repetitive DNA because it clearly shows where the coding DNA ends. Repetitive DNA is also commonly used inside the gene to give more variety to the gene. It is possible that after the telomeres are destroyed, their nucleic bases are inserted into the gene. (also i think it's pretty ironic that the code for telomeres in humans more or less spells out TAG)

    3) Telomeres are built by the enzyme Telomerase, but how long they are is determined by a specific locus on the chromosome.

    4) Telomeres determine when the cell goes through apoptosis. If a cell divides enough times, the telomeres become too short, and the chromosome will no longer be able to replicate during mitosis. Instead of dividing anyway (which could cause some pretty nasty defects, including cancer) the telomere tells the cell to commit suicide.

    5) like someone said earlier in the blog, because telomeres are repetitive, when a piece of telomere goes missing, the telomere still works because there are still repeating sequences left. Furthermore, the time-bomb-like feature of telomeres wouldn't work if they were made of a single sequence. Any shortening of the telomere would cause the cell to immediately undergo apoptosis, and that wouldn't be good. With this design, telomeres are stable clocks that determine cell life.

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  22. 1: Telomeres protect the end of the DNA by covering them, which doesn’t allow the DNA to protect the end of the chromosome from deterioration or from fusion with near by chromosomes.
    2: Repetitive are just DNA sequences that are repeated in the genome. Repeating DNA sequences are used to format expression of unique coding sequence files and to organize additional functions essential for genome replication and accurate transmission to progeny cells. Repeating elements also can serve as initiators or boundaries for heterochromatin domains and provide a significant fraction of scaffolding/matrix attachment regions (S/MARs) suggests that the repetitive component of the genome plays a major architectonic role in higher order physical structuring.
    3: There are many factors that contribute to the length of telomeres. Factors including: age, paternal age at birth, and sex.
    4: Telomeres are related to cell function because they contribute to successful cell division because they cap the end-sequences and then they themselves get lost in the process of DNA replication.
    5: Nothing created by God is an accident. Even if the purposes and functions haven’t been discovered yet there is always a purpose for it because God didn’t create anything without a purpose. I think that there is some sort of advantage of the design because the telomeres have a specific purpose in cells and then they are able to lose themselves because they have accomplished their purpose.

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  23. Telomeres protect a cell's chromosomes from fusing with each other. They act as a cap to prevent the loss of genetic information during replication. Thus, telemores function to guard chromosomes against degradation, fusion, and rearrangements during replication.
    The telomere-associated proteins are important for maintaining telomere stability and regulate length. These proteins may be the cause in the various lengths of the telomeres.

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  24. Some bacteria have telomeres, so from one perspective it looks like they were handed down via evolution. Why use what appear to be accidental sequences to make the ends of chromosomes? Is there some advantage or design feature inherent in these chromosomal pieces?
    the cap acts as the protective enclosure that will prevent the loss of important genetic information while replication is in process. What is know of telomeres is that they function to protect and guard the chromosomes from rearrangements while replication is going on.
    Telomere also has associated proteins that maintain telomere stability, they are also repeats itself. So when a strange is short then the telomere comes in and fixes the gap.

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  25. Telomere's protect DNA by making sure that chromosomes don't accidentally attach to each other. This is very important for the life of a cell. Repetitive DNA are sequences that are repeated in the genome. These sequences do not code for protein. Repetitive DNA sequence elements are crucial for molecular interactions forming nucleoprotein complexes.The size of the chromosome has a factor on how long the telomere is. Also how fast the replication fork moves and the size of the templates determine the size of the telomere. Telomere's are related to cell function because if the cell would not function without telomere's because telomere's are crucial in not allowing chromosomes to accidentaly bind to each other. Even though it seems as though telomere's are accidental pieces for the chromosome, I believe they were meant to be at the ends of chromosomes because they fit perfectly at the end of the chromosome and this can happen under certain conditions and these conditions are when the DNA polymerase is moving in a 3'-5' direction.

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  26. 1) every time DNA is separated to be replicated, an enzyme must cut through something in order to separate the DNA. Instead of cutting into the part of the DNA that has information that cant be damaged, the enzymes cut into the telomeres, which don't contain any important information.
    2) The reason telomeres are made from repetitive DNA is because repetitive information is not as vital to keep intact as non-repetitive information that could be lost.
    3) The lengthening of telomeres is determined by an enzyme called telomerase.
    4) Telomeres are involved in cell division. They allow DNA to be separated without damaging any information, which would lead to a mutation.
    5) There would appear to be intelligence behind this as seems is the case with all of creation. It's the same picture we see with all of cellular life, the smallest change, such as non-repetative sequencing in the telomeres, would compromise the entire system and cause disorder.

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  27. I discovered in my research that telomeres protect DNA by making up for the incomplete replication in DNA that occurs at the chromosomal ends.

    Telomeres are very important in cell function in that they, in a way, form a "cap" on the end-sequences of DNA. When this occurs, it gets lost in the process, but it has an enzyme that adds repetitive necleotide sequences to the ends of the DNA. This enzyme is called telomerase. Also, this very enzyme replaces the cap that it forms on the end of the DNA sequences.

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  28. 1.Telomeres allow the cell to recognize the difference between regular DNA and damaged DNA. When the telomere stops functioning correctly, it causes the DNA to be destroyed. This means that the telomere essentially protects the healthy DNA from being destroyed. Also when malfunctioning DNA is allowed to exist it can cause genome instability and cause the cell to stop functioning. The telomeres in essence eliminate the flaws in the DNA.
    2.I think it is possible that the reason that telomeres are made out of repetitive DNA is that when the proteins mRNA is created, and much later on in the process, the protein is made, it allows for a useless codon to be added on, thus not hurting the DNA by accidentally adding on a codon which could change the protein made.
    3.The length of telomeres is an indication of diseases, stress, and aging. The shorter the telomere the harder it is for it to duplicate, thus the older the cell, the shorter the telomere.
    4.Telomeres cap the DNA replication, and has been hypothesized to prevent cancer. It also prevents for important DNA sequence from getting lost in an excess of DNA.
    5.These accidental sequences allow for important DNA from getting lost, as well as prevents the DNA from floating away, as they anchor the DNA.

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  29. 1. I found this abstract that brief but helpful for me in answering how telomere’s protect DNA: “Telomeres allow cells to distinguish natural chromosome ends from damaged DNA. When telomere function is disrupted, a potentially lethal DNA damage response can ensue, DNA repair activities threaten the integrity of chromosome ends, and extensive genome instability can arise. It is not clear exactly how the structure of telomere ends differs from sites of DNA damage and how telomeres protect chromosome ends from DNA repair activities. What are the defining structural features of telomeres and through which mechanisms do they ensure chromosome end protection? What is the molecular basis of the telomeric cap and how does it act to sequester the chromosome end? Here I discuss data gathered in the last few years, suggesting that the protection of human chromosome ends primarily depends on the telomeric protein TRF2 and that telomere capping involves the formation of a higher order structure, the telomeric loop or t-loop.” I didn’t want to pay for this guy’s article though so I don’t know the details of his paper.
    http://www.ncbi.nlm.nih.gov/pubmed/11850778
    2. Repetitive DNA: DNA sequences that are repeated in the genome. These sequences do not code for protein. One class termed highly repetitive DNA consists of short sequences, 5-100 nucleotides, repeated thousands of times in a single stretch and includes satellite DNA.
    http://www.medterms.com/script/main/art.asp?articlekey=5309
    There are clear theoretical reasons and many well-documented examples which show that repetitive, DNA is essential for genome function. Generic repeated signals in the DNA are necessary to format expression of unique coding sequence files and to organise additional functions essential for genome replication and accurate transmission to progeny cells. Repetitive DNA sequence elements are also fundamental to the cooperative molecular interactions forming nucleoprotein complexes.
    http://www.ncbi.nlm.nih.gov/pubmed/15921050
    “Telomeres are made of repetitive sequences of non-coding DNA that protect the chromosome from damage” That was the best explanation I could find of the function of the repetitive DNA that made up the telomere.
    http://ghr.nlm.nih.gov/glossary=telomere
    3. Telomere’s protect the chromosomes from unraveling, they act as a “cap”…they are essential to cell function because if the chromosomes unraveled then the DNA function would not work correctly and the nucleus would become crowded with tangled loose DNA strands…I assume this would hinder the process of cell reproduction occurring also.
    4. The telomere’s advantages are numerous, they allow for change within the dynamic system of cell division/replication and function. The telomeres do not code for proteins, and they have the ability to shorten when necessary. They provide stability for the chromosomes, but allow for proper cell reproduction by being able to drop off the end during that process.

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  30. 1 How do telomeres protect DNA?

    they seem to protect the DNA from being damaged when cut but then they also protect the DNA from fusing to gather and causing mutations in the DNA chain. it also it the repair system for the DNA so if it is interrupted it could potentially cause a mutation in the DNA.

    2 What is the significance of telomeres being made from repetitive DNA? (what is repetitive DNA and what is it good for?).

    this seems to show the Evidence that repetitive DNA plays a role in chromosome pairing is possible yet another one of the many branches of the Telomeres. in more depth the Telomeres function by preventing chromosomes from losing base pair sequences at their ends.

    3 What determines how long telomeres are?

    this is determined due to every time a cell divide the telomeres get shorter so once it gets to a certain length it causes the cell to stop dividing, so telomeres are similar to how many rings there are in a tree trunk after it has been cut down.
    4 How are telomeres related to cell function?

    A telomere is a repeating DNA sequence,it helps in the replication of the DNA and it also causes the genes to stay clean and orderly.

    5 Some bacteria have telomeres, so from one perspective it looks like they were handed down via evolution. Why use what appear to be accidental sequences to make the ends of chromosomes? Is there some advantage or design feature inherent in these chromosomal pieces?

    these chromosomal pieces are what is providing the process of cell aging in that way the cell can't get to old and start losing parts while still replicating which then would bring about the making of mutated genes/cells.

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  31. 1. Telomeres protect DNA by acting as a buffer zone where DNA can be lost without losing important gene information. The DNA polymerase protein complex cannot replicate the sequences at the ends of chromosomes , therefore, without telomeres a portion of the genome would be lost with each replication cycle. The telomere’s role is to be discarded instead of the genes, which protects the cell’s genetic information.
    2. Repetitive DNA may be used because it is easy for the cell to replace the telomeres if they are lost. Also it prevents coding of possibly harmful proteins if just random nucleotides were put together. This would definitely be an interesting area of study to pursue in the future.
    3. The lengthening of telomeres is accomplished by the enzyme telomerase. Several determinants of telomere length include age (older people have shorter telomeres), paternal age at birth (babies with older fathers have longer telomeres), and gender (men have shorter telomeres). Also it has been shown that oxidative stress decreases the length of telomeres.
    4. Telomeres are important to cell function because they dictate the life of the cell. If the cell has no telomeres then genes will be lost and the cell won’t be able to function so it will die. If the cell has long telomeres it will be able to survive and replicate many times. Also telomeres prevent the fusion of DNA strands. If DNA strands came together, protein products would be significantly altered, probably enough to result in cell death.
    5. When looking at bacteria and considering evolution you face the question of why would an organism go from circular DNA to linear DNA when the linear DNA requires telomeres to be successful? Evolution demands that DNA and telomeres to evolve at the same time, which is impossible. Therefore, telomeres point to a Designer who put them on the ends of DNA in order to protect the valuable gene information.

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  32. The telomeres protect the chromosome from fusing together with other DNA structures. They also cap the end of the sequence for organization and protection from getting lost. The repetition of DNA is important for cell division and copying the DNA into the daughter cell. The telomerase caps the end of the chromosome and prohibits the coping enzyme from continuing past the end point and excessive information. Telomeres are important because they increase the lifespan of the cell. When taken out of an infant and cultured, the cell divided almost one-hundred times, but when taken from an eighty year old, they only divided a couple dozen times before the cell quit dividing. Telomeres are snoRNA signals that “provides an AAUCCC (in mammals) template to guide the insertion of TTAGGG” (http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Telomeres.html). I think something this crucial to the cell could not be accidental. It seems without telomeres, the “first cell” would have replicated to much of the chromosome, or even the chromosome would have lost part of its sequence and not have divided properly. Evolutionists might argue that the cell would have used it for survival of the fittest concept and what seemed to be an accident helped it survive, but I don’t see how the first cell would have survived without it.

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  33. 1. Telomeres prevent the adhesion of chromosomes and the fraying of DNA which would result in it not being transcribed as it would be interpreted as damaged.

    2. Repetitive DNA is several genes coding for the same substance. It affects the organization and quantity of nucleoproteins.

    3 & 4. The length of a cell's telomeres is determined by its function. Somatic cells have a set amount of telomeres (about , while germ cells have telomerase that sustains its telomeres for much longer. It has been found that the telomere length of human offspring is affected by paternal age; this is probably linked to the maintenance of telomeres by telomerase and how it changes through an individual's life. Because sperm cells are produced continually, telomerase action must continue steadily to result in the same telomere length of offspring. However as seen in "Paternal age at birth is an important determinant of offspring telomere length" in Human Molecular Genetics, this is not the case.

    5. Telomeres are simply DNA that does not code for anything. They do not require synthesis which means they are always present unless DNA is replicating, or has just replicated. This makes them useful for protection of the DNA.
    In evolution, bacteria with linear DNA, and telomeres, may be the suggested ancestors of eukaryotes. That which makes the circular DNA circular may have becoome redundant in linear DNA and formed telomeres. However, my question would be: why would bacteria with circular DNA evolve into bacteria with linear DNA? Perhaps it is related to the less complex process of transcribing linear DNA. This is funny--more complex (in this sense) becoming less complex. This is the inverse of evolution--de-evolution.

    http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Telomeres.html
    http://www.ncbi.nlm.nih.gov/pubmed/15921050

    http://hmg.oxfordjournals.org/content/16/24/3097.full

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  34. 1-2) Telomeres are crucial to the life of the cell. They keep the ends of the various chromosomes in the cell from accidentally becoming attached to each other. Although they are made of the bases, they do not encode proteins, but rather are just meaningless information. They prevent the ends of the DNA that do matter from suffering damage and prevent the chromosomes from forming rings or binding haphazardly to other DNA. Also when the chromosomes are being copied by enzyme molecules, the enzymes are not able to fully copy the ends of the chromosomes, thus the telomeres help retain as much of the original copy as possible.

    3) Telomeres naturally erode over time after many replications of the chromosomes; they reach their Hayflick limit. An enzyme named Telomerase which are partly protein and partly RNA are capable of slowing Telomere erosion or lengthening the actual telomere themselves.

    4)Because telomeres keep cell's information encoded in the DNA from being cut off during their copying, telomeres are very important in the cell's life. Also telomeres are involved in the stopping of cancer. Cancerous cells, after copying their malignant forming DNA, would eventually reach their Haflick limit, but the telomerase lengthen the telomere causing the cancer to keep replicating. This is very strange as in a helpful part of cell division actually benefits the growth of cancer.

    5)Naturally as time goes on, the DNA would not be able to replicate itself correctly. Instead of just "throwing it away", cells could just attach it to the end of the chromosome as a telomere after making an acceptable and correct copy. I think this seems like a recyclable program sort of like for cans and bottles.

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  35. 1.) They essential for cell function they are found at the end of chromosomes and they stop the genes from basically unraveling and causing widespread mutation. much like other cap proteins we discussed in class in prior lectures.

    5.) I don't know why evolution supporters would use this as an example because the telomeres actually don't promote mutations they stop the genes from changing and thus if there is no change in the gene there cannot be any mutation this seems to be a indicator of design rather than random mutation.

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  36. The ends of chromosomes are protected by Telomeres which defend the chromosomes from cell death or senescence. By protecting the chromosome ends, prevent the loss of genes during cell replication. Every time a cell replication process happens the telomeres get like stress which gradually lessens the telomeres lifespan, this would shorten the telomere which is not a positive thing.

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  37. 1 How do telomeres protect DNA?
    the telomeres helped o protect the cell from deteriorating, unraveling, or fusing with other chromosomes.


    2What is the significance of telomeres being made from repetitive DNA? (what is repetitive DNA and what is it good for?).
    repetitive DNA is where the substrings of the genome repeat multiple times. this serves as a structural aid. this makes up for mistakes that might happen, that way it can corrects itself or be corrected.


    3 What determines how long telomeres are?
    it is a specific set of enzymes. They are determined heretically as well. They can fluctuate a little bit. once it gets to small the cell dies.


    4 How are telomeres related to cell function?
    telomeres help determine the timing for apoptosis. it shortens when it needs to kill the cell and then the cell dies.


    5 Some bacteria have telomeres,  so from one perspective it looks like they were handed down via evolution.  Why use what appear to be accidental sequences to make the ends of chromosomes? Is there some advantage or design feature inherent in these chromosomal pieces?
    they are in no way accidental. they serve a specific function. why them? i don't know. i don't make the rules, however the telomere just knows when the cell's time is up. it wouldn't just accidentally start doing that. it is purposefully placed.

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  38. The telomeres are repeated DNA sequences located at the ending of chromosomes. Telomere protect chromsome from fusing with neighbouring chromosomes. Teolomeres are disposable buffers, teolemeres add repetitive nucleotide sequences to the ends of DNA after the "cap" lost in the process of replicating, since DNA polymerase cannot replicate the sequences of the ends of chromosomes. Mutated telomere will cause cancer. "Telomeres compensate for incomplete semi-conservative DNA replication at chromosomal ends." The length of telomere are varies between species. Eukaryotic tolomeres are 3 inches long that allow telomere to maintance and capping.

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  39. Learn more details about |DNa/RNA here
    http://biochemhelp.com/category/biology/dna-and-rna

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  40. Hei i have some Sugestions for articles you could have in deep. 


     I wonder about defence memory cells and the naive cells.I read the first are growing in number when we get older and decrease the number of the seconds.A reason to bad health of old people?.Have you consider the biocatalizators that can clean the cells from the toxines and let them like new? Im thinking also about something that block the hydrolyse of the 1-4 bond of carbohydrates to avoid inntake of glucose. I readed NER repair is the way to go younger and   Stronger(even telomerase).Have you analyzed what is in the blood of the young rat of the experiment of 1950 that the old rat dont have? We could be very happy of having it in the right dose. There are substances as UDP gluconarate and a needed vitamin or coenzyme that can clean the body and help smokers. Have you made analyses to find out how work the metabolism of a breather (those that almost dont eat for long periodes).I found it very interesting. 


    Regards.A reader

    Sendt fra en Samsung Mobil

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