Genetics and fingerprints

  1. Identical twins have identical genetic codes. [Some if not all]* Identical twins also have different finger prints. This induces me to wonder if finger prints are a result of the genetic code or not. If the genetic codes of identical twins are identical, then, if finger prints are manifested from the genetic code, then their finger prints should also be identical. But apparently that is not true. Could it be that (this idea may sound rather outlandish) finger prints developsaccording to the environment like personalities? Could the finger prints of two identical twins be identical at birth but eventually change? Well, I know the aforementioned questions suggest awkward conclusions, but that's what occured to me when the problem 'introduced itself' in my mind.




    *I'm not sure whether or not this fact applies to all identical twins or only some. If my presentation of this assumed fact is incorrect, please do the honors of correcting me.
     
  2. jcsd
  3. Monique

    Monique 4,699
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    Fingerprints of identical prints are not identical, they develop under the influence of stochastic factors: involving chance, probability, containing a random variable.
     
  4. If identical twins have the same exact genetic composition, and their finger prints are not the same, then one can conclude finger prints are not directly related to the genetic code.
     
  5. Monique

    Monique 4,699
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    Right, but making such conclusions isn't always easy though :)

    For instance, there is a genetic disease that is a lysosomal storage disorder where an identical twin was documented where one was ill and the other was not. Both had the same mutation in the gene that causes the disease. What happened is that likely one got a more severe infection early in life that caused more storage material to accumulate in the lysosomes, beyond a level that could be cleared by the patient. The other always just stayed below the critical level and thus had no symptoms.

    So that is a case where a genetic mutation in a gene causes a disease, but the penetrance is not 100%, so one gets sick and the other does not.
     
  6. Forgive me if this is a stupid question, but how do we know that identical twins have identical genetic makeup?
    Has someone actually read, recorded and compared all 3 billion base pairs in the DNA of sets of identical twins?
     
  7. Monique

    Monique 4,699
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    Genetic twins come from a single fertilized egg that after a few divisions split into seperate clumps of cells and developed seperately. Since they came from the same fertilized egg, they are genetically identical. Ofcourse, mutations are introduced in the genome during mitosis, I'm not sure about the rate. But since only 3% of all DNA is coding you can be pretty sure that they are as identical as can be.
     
  8. That is truly intriguing. So identical twins aren't quite so identical? Is that what this tells us?
     
  9. loseyourname

    loseyourname 3,632
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    They are identical genetically, but genes are selective expressed and expressed to differing degrees depending on circumstances both under the control of others genes and, more importantly, not under the control of any genetic factor or, for that matter, any factor internal to the organism.
     
  10. What characterizes an internal factor? an external factor? What differentiates the two?
     
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