[Helen Zhou]

Helen Zhou  asked the Naked Scientists:
   
Dear Naked Scientists,

When two identical twins are conceived, is their DNA then exactly identical?

And if so, won't this change later on as the DNA mutates slightly?

Thanks
Helen

What do you think?

[Chemistry4me]

Yes, they are genetically identical.

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Identical twins are never quite identical because no two individuals have identical environments (living conditions).

[JnA]

Most inconsistencies in twins occur in utero. Like fingerprint formations...

[Chemistry4me]

Really...?

[JnA]

well, simplified, yes. There's some phenotype action going on too... but generally identical twins share the same DNA (eg a DNA test would not be able to pick them apart) and differences are from in utero conditions.