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Identical Twins: fingerprints and DNA....

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Identical Twins: fingerprints and DNA....

Postby TheTosh » Wed Jul 20, 2005 12:08 am

How do they differ? If so, why do they differ?

Is it possible for two people to ever have had or have the same DNA? I mean there has to be a finite number of combinations...or is it just that this many humans havent yet lived?

How do the fingerprints of parents and siblings compare to a persons? Are they closer to the person than most others like the DNA or does it currently seem random?


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Postby Betsy » Wed Jul 20, 2005 6:12 pm

I came across this item a couple of weeks ago: From Eurekalert

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Postby TheTosh » Wed Jul 20, 2005 9:13 pm

'Scientists think that chemical exposure, dietary habits and environmental factors may all have epigenetic affects'. Does that not mean that someone cannot be identified by DNA because it is variable over time. That article basically says that the genome trace of two identical twins is more different if they are older.
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Postby Betsy » Thu Jul 21, 2005 12:20 pm

I think that it's not so much differences in the DNA, but where and how much the DNA is methylated. That is, where a methyl group (CH3) is added to the DNA. And from that article the scientists plan on figering out how DNA is methylated.

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Postby MrMistery » Thu Jul 21, 2005 6:51 pm

DNA sequence does not change during a man's life
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Postby Daniel Tillett » Mon Jul 25, 2005 6:18 am

It is not quite true that DNA doesn't change during a persons life (if it didn't there would not be cancer). However, for practical purposes you can assume that if you take a sample of DNA from a person now and again in 20 years that they will be identical. This is because a persons genetic profile is constructed from many thousands to millions of copies of each DNA fragement so that any mutations in any one cell are averaged out.
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Postby chemistry_freako » Tue Jul 26, 2005 5:09 am

Yea - exposure under the sun might result in alterations in DNA. Alterations in our DNA in our lifetime range from point mutations, to thymine dimers and etc..then again, there're also carcinogens and polyomaviruses?
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Postby mith » Tue Jul 26, 2005 5:30 am

Don't forget telomeres.
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Postby TheTosh » Tue Jul 26, 2005 3:40 pm

Are these variations so small that a DNA sequence will still be different enough from all other people's DNA then?
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Postby zami'87. » Wed Jul 27, 2005 1:10 pm

It is possible to find differences in identical twins if the mitochondrial DNA is tested.
In addition, the expression of genes in monozygotic twins can be different. For example, a minor infection can trigger the genes that code the immune system to respond in different ways, resulting in different antibody protein molecules to be found in each twin. Mutations and rearrangement of pieces of DNA can slightly change as the twins grow, causing differences.

Female monozygotic twins can also differ because of X inactivation.


from article:
http://mypage.direct.ca/c/csamson/multi ... tical.html



Mutations are more frequent in mtDNA than in nuclear DNA. That's also major problem in aging process.
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Postby MrMistery » Wed Jul 27, 2005 7:35 pm

So the differences in the mtDNA are because mutations arrise here more often? Because other than that, i don't see why, considerating that they both come from the mother
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