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Chromosomes, Genes and DNA

  1. Aug 25, 2004 #1
    Way back in the dark ages when I went to high school, we where taught that humans had 32(?) chromosomes and that each chromosome contained individual genes which was what actually passed on characteristics and traits like eye color etc. So now there is DNA and the humane genome is billions of bits, links, whatever long.

    So how does DNA relate to chromosomes and genes? I understand that genes are actually segments of the DNA molecule; but, what is the relationship if any between chromosomes and DNA molecules? Does each chromosome contain one complete molecule of DNA or are chromosomes completely out of the picture now? (Yet they still talk about X and Y chromosomes and genes carried on or within or attached to them.)
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  3. Aug 25, 2004 #2


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    There's 23 chromosome in human.

    Here some definition that might help you

  4. Aug 26, 2004 #3
    Okay, thanks for the information, but my question remains partially unanswered. Does each chromosome contain one whole seperate strand of DNA or is there just one strand in each cell that are seperate bundled packages of segments of the one DNA strand per cell? Is there one strand or are there 23 seperate strands one for each chomosome per cell?
  5. Aug 26, 2004 #4


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  6. Aug 26, 2004 #5


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    Another way to think about it that might help...
    You'll have 46 strands of DNA in each cell. Think of them as threads.
    These threads pair up, so you have a total of 23 pairs of strands.
    On each of these threads, you have many genes (think of them like a lot of knots tied in the thread...a poor analogy, but a good visual...or like multicolored thread, each segment of color is a gene).
    Now, those long pieces of thread get wrapped around spools (the spools are histones) to condense the unruly threads into a smaller and neater arrangement.
    This entire combination of paired threads wrapped around spools is called a chromosome. Since you had 23 pairs of threads to start, you have 23 chromosomes.

    There are some times during meiosis, which forms eggs and sperm, when those pairs of threads separate and the single threads go to two different cells. In that case, the single thread is also called a chromosome.

    One last thing to remember, because this usually trips people up. When you look at a piece of thread, you know how it's actually two or more threads intertwined? In this analogy, think of each DNA thread as actually containing two fibers (I'm using "fibers" to avoid re-using the term thread, and confusing the analogy further), those two fibers are the double helix structure you hear about.
  7. Aug 27, 2004 #6
    Thank you, all of you. for the information. I think that I have a better understanding now. This has bothered men for sometime as I have never seen or read before the relationship between chromosomes and DNA.
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