There is no such thing as identical where twins are concerned

Identical twins have identical genomes, but that is where it stops. There are subtle differences in their personalities, how they look, how they act and in their susceptibility to disease. How can this be?

It all depends on how the “epigenome” is modified by the environment, say scientists from Sydney’s Garvan Institute of Medical Research and Queensland Medical Research Institute, who have just completed an 8-year study involving 512 adolescent twins (128 identical twin pairs, as well as 128 non-identical twin pairs), with an average age of 14.15 years.

More specifically, it depends on exactly how particular parts of the are affected by ‘methylation’, or the attachment of hydrocarbon molecules - ‘methyl groups’, that literally change the voice of the genome, silencing some genes and amplifying others.

Garvan epigeneticists Dr Marcel Coolen and Professor Susan Clark focused on the methylation profiles of a group of ‘imprinted’ genes that are important in the control of growth during early development. They found differences in the methylation profiles of these imprinted genes, even in genetically identical twins. It is these changes, they say, that probably give rise to differences we observe in identical twins. Their findings are published in the International journal PLoS One, now online.

“The aim of our study was to understand what role genetics plays in determining who we are, versus the role of environmental factors,” said project leader Professor Susan Clark.

“We compared genetically related people with genetically identical people, seeing how closely their methylation patterns matched.”

“Our findings support the hypothesis that changes in methylation reflect the interplay between the environment and genetics.”

“We showed that methylation patterns are exquisitely inherited, and so the methylation patterns of are still very similar to each other. This demonstrated that the DNA sequence does instruct the methylation pattern. When that methylation pattern changes, however, it gives rise to potential changes in phenotype, or who we are.”

“This is one of the largest studies ever undertaken of this sort, and these are challenging studies, so having proof of principle is important.”

“We now have evidence that changes in methylation patterns occur in genetically identical people and therefore these changes can potentially change disease . The next step will be to examine twins that are discordant for a particular disease – such as Type 2 diabetes. In those cases, we will be looking for discordance in methylation of the key genes.”

Provided by Garvan Institute of Medical Research

5 /5 (2 votes)
add to favorites email to friend print save as pdf

Related Stories

Hereditary cancer risk

Aug 16, 2011

(Medical Xpress) -- Medical researchers have discovered a new type of mechanism causing cancer susceptibility, showing that tiny changes in some anti-cancer genes can act as magnets to attract modifying "biochemical tags", ...

Seeing double (or triple) in genome sequencing

Mar 28, 2011

Identical twins have always been assumed to be exactly that – identical, right down to the genetic level. But a new study by University of Western Ontario molecular geneticist Shiva Singh and his colleagues say this ...

Naughty children - it's nature and nuture

Jun 07, 2011

(Medical Xpress) -- Disregarding the rules and confrontational behaviours are commonplace with young children and can even arise in the first year of life. For some children, this trend will persist and become ...

Recommended for you

Neutralising antibodies for safer organ transplants

19 hours ago

Serious complications can arise following kidney transplants. If dialysis is required within the first seven days, then the transplanted organ is said to have a Delayed Graft Function (DGF), and essentially ...

User comments

Adjust slider to filter visible comments by rank

Display comments: newest first

ArtflDgr
1 / 5 (3) Oct 14, 2011
what they are trying to say is that identical people in different lives are not identical because they have diffeent lives...

ie... two cars off an assembly line are different cause one is in the nevada desert and one has a life in ny... and the dirt on the hood is different... its nurture...

soddy... thats always been inane...
but it takes a phd to make it sound like its critical..

if one thinks of the first two cells as the same, the rest is weathering as they exist in a different place than another.

ok... next problem
how do they resolve that with their marxist equalism?

if even identical twins are not the same
then how can people who arent even from the same continent be the same?

cogency is not the high point of ideology..
but also, such inane views explain why Schadt was able to claim that after 50 years, they have nothing, no actual theory or map.. just tons of facts and incongruent ideas aligned with ideology... VERY SAD!!!!
RobertKarlStonjek
5 / 5 (1) Oct 14, 2011
There are four different types of identical (monozygotic) twins:
Dichorionic-Diamniotic [Separate chorion (outer membrane surrounding embryo)-Separate amniotic Sack]
Monochorionic-Diamniotic [Shared chorion-Separate amniotic Sack]
Monochorionic-Monamniotic [Shared chorion-Shared amniotic Sack]
Conjoined Twins
hush1
1 / 5 (1) Oct 14, 2011
Congrats to all involve.
I wanted to be the one asserting the causality of methylation.
Envious of your laurels. And happy about it.