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DNA possobilities

  1. May 8, 2007 #1
    I have a few questions about the dna strand and how long is it. When the dna strand changes through generations is the strand growing longer or is it just changing. Basically does it have a limited amount of data or does it just keep getting more complex.
  2. jcsd
  3. May 9, 2007 #2

    jim mcnamara

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    Staff: Mentor

    There is no best answer for this, as far as I can tell.

    Ferns, for example, have a LOT of DNA, they often have over 1000 chromosomes. Many are duplicates, because ferns are highly polyploid. So I guess this could mean that some fern species never got rid of "extra" DNA.
    So maybe they changed over time by just adding more DNA.

    Then there are introns, which are often considered DNA spacers with a possible error-checking function, inside the DNA strand. Introns do not code for proteins. Some species have a lot of introns in total DNA. Exons are what is leftover in the DNA strand when the introns have been "peeled off". Exons can be less than 60% of the total DNA. It is likely the introns are for a reason, but they do represent a change that is kind of like "fiber filling", sort of a do-nothing or copy-proofing addition.

    Mutations are thought occur in many ways - moving the position of a gene on a piece of DNA, deleting base-pairs in a gene sequence, changing base-pairs in a sequence, adding extra base-pairs, moving genes from one non-homologous chromosome to another, duplicating/deleting whole chromosomes, and so on.

    So I don't see just one pattern that leads to changes, DNA in a nucleus can grow or shrink, or become less complex with the addition of introns, or much more complex like in the fern.
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