Expert: Christopher Rosch - 1/6/2006

Question
I have one question concerning monozigotic twins. It is often said that they have identical DNA,but isnt it true that due to some quantum fluctuactions in the development of an organisam there are some differences,too small for the DNA detector,but enough for some difference? I am asking this since I am a member of a TOEquest forum,and I am very interested in the relations between "human mind"-biochemical reactions and electric impulses in the brain.This is all related to the DNA,and it would be plausible to me that monozigotic twins have like 99.99% the same DNA,but there must be like 0.01% difference!(Since from where I am standing "human mind" and body are different manifestation of the same thing,there is no dualisam.If they have 100% identical DNA,wouldnt this be a violation of the theory that mind and body are different mainfestation of the same thing? I think the same concept can be applyed on potential clones.  Please tell me am I right,does this make any sence?
Thank you on your answer!
Regards!

Answer
Hello Marko,

monozygotic twins do have identical DNA. There are no differences in DNA that cannot be detected by modern molecular techniques (PCR based methods, DNA sequencing et cetera). The basic building blocks of DNA are four "bases" (A, C, G or T) and the sequence of these bases can be read by molecular biologists. The genetic information is firmly kept in that DNA sequence ("chemical storage"), not in some physical parameters like orientation, conformation, angles, distances or similar properties (which indeed would suffer from quantum effects).

The only possible event resulting in differences on DNA level in both twins is a mutation in earliest development (zygote stadium, but after twinning). However, such mutations are extremely rare: a common type of mutation, a "point mutation", would result in about 0.000000000003% difference (but keep in mind that most mutations have no effect while some are lethal; only a small percentage of mutations shows any effect at all). Furthermore mutations affect only the descendents of the cell which showed the mutation first. So, mutations that occured during embryonal development would not be found in each cell of the body.

On the other hand identical twins can be distinguished by looks - at least by the parents. But this is not due to differences in the DNA but a result of different environmental influences. These influences -- the sum of all events an individual experiences -- begin in the womb and are unique for each individual and can in no way be reproduced. Even twins which are permanently together make different experiences, even if the only difference lies in the "data processing" in the mind.

Many traits like body height or stature strongly strongly depend on environmental factors, while others like eye color are predetermined by the genes. In my opinion the "human mind" (including intelligence and emotions) is extremely dependent on environmental influences. At the same time the mind's biological basis, the brain tissue, is determined mainly by the genes. In an adult brain the mind affects the brain tissue as much as the architecture of the brain influences the mind. So, in my opinion there is no mind-body dualism, but both are part of the same, a "human being".

When discussing clones it is often neglected that clones do not inherit the influence of environmental factors; all the experience made by a donor is lost when cloning her.
In fact, identical twins are the best example for studying clones - by definition clones share identical DNA and that's the case in monozygotic twins!

Best regards,
Christopher