DNA

Discussion in 'Forensic Science' started by Calihan, Mar 9, 2008.

  1. Calihan

    Calihan Captain

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    I have a question about DNA.

    I'm a little confused about something can you get DNA from sperm or semen or can you get it from both?

    It seems as if in the show and in novels they say DNA is extracted from sperm but sperm is only a small part of an ejaculation.

    So is DNA in sperm, semen or both?
     
  2. allmaple

    allmaple Judge

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    the sperm are the actual little swimming cells that contain the dna. semen is the sperm and fluid. so technically semen has dna because it contains the sprem, but i believe that the sperm are the only actual cells in there so the dna is contained within them.
     
  3. adorelo

    adorelo CSI Level Two

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    As sperm calls are reproductive cells, they contain only half of the DNA of the man. Obviously, half is generally enough to be able to match it to another sample, but I thought you may like to know.

    As for the semen as a whole entirety, I'm not sure. I'm not sure if the sperm is the only thing there, or if the entire thing is made up of other parts like water, salts, etc. If Ken doesn't pop in here (I'm sure he will though) I'll attack him via PM ;) (I'm kidding, of course).
     
  4. Calihan

    Calihan Captain

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    Thanks guys I have an answer, for adorelo this is typically in semen besides sperm.

    While we sometimes refer to semen as "sperm," sperm cells (spermatozoa) actually constitute only about 10% of our total ejaculate. That 10% contains from 200 million to 500 million sperm cells, though the figure can be higher for younger males due to the pubescent production of androgen hormones, such as testosterone, which also trigger the growth body hair and the lowering of the voice. (Remember: It takes only one sperm cell to fertilize an egg and make a baby.)

    The remaining 90% is referred to as seminal plasma. (Plasma is defined as a fluid that carries a suspended solid, whether it's blood "fluid" carrying blood cells, or semen carrying sperm.) Composition of seminal plasma varies among individuals, and even in the same individual from time to time. It contains some 30 substances (many in minute quantities); some are produced by different parts of our male anatomy, and some are by-products of body functions. They include:

    • ascorbic acid (vitamin C, for tissue maintenance)
    • blood-group antigens (from immune system)
    • calcium (mineral)
    • chlorine (oxidizing agent)
    • cholesterol (steroid alcohol present in body fluids)
    • choline (base, part of the vitamin B complex)
    • citric acid (occurs during cellular metabolism)
    • creatine (nitrogenous substance found in muscle)
    • deoxyribonucleic acid (DNA)
    • fructose (sugar used for energy)
    • glutathione (peptide amino acid)
    • hyaluronidase (enzyme)
    • inositol (sugar found in muscles)
    • lactic acid (byproduct of muscle use)
    • magnesium (mineral)
    • nitrogen (gas found in all living tissue)
    • phosporus (mineral)
    • potassium (mineral)
    • purine (compound of uric acid)
    • pyrimidine (organic base)
    • pyruvic acid (formed from either glucose or glycogen)
    • sodium (salt)
    • sorbitol (body alcohol)
    • spermidine (catalytic enzyme)
    • spermine (ammonia compound found in sperm)
    • urea (from urine)
    • uric acid (from urine)
    • vitamin B12 (for proper function of nervous system and metabolism)
    • zinc (mineral
     
  5. adorelo

    adorelo CSI Level Two

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    ^^ That's why I dorpped out of med school. Haha. I did know that, I just wasn't sure if there was any DNA in it :lol:

    But thank you honey. Where'd you get it from. You should state your source.

    Thanks again

    Jodie x
     
  6. KenGoddard

    KenGoddard Hit and Run

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    You don't need me on this one. As everyone seems to understand, the DNA strands are in the heads of the sperm cells.
     
  7. KenGoddard

    KenGoddard Hit and Run

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    Forgot to add that the issue gets more complicated when you examine samples from a sexual assault kit and have to take into account the victim's DNA (epithelial and white cell sources).
     
  8. adorelo

    adorelo CSI Level Two

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    But, isn't is fairly easy to distinguish between the two if the victim is female and the rapist male? X and Y and all?

    And we always need you, Ken. :)
     
    Last edited: Mar 10, 2008
  9. KenGoddard

    KenGoddard Hit and Run

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    Yes, relatively easy ... and kind of you to say so. :)
     
  10. Dizzney

    Dizzney Moderately Insane Moderator

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    Bumping up for people who want to talk about DNA
     
  11. DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).

    The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.
     

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