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It is near the millenium and there is great enthusiasm over the decoding of the code of life. We all had great expectations about the Human genome Project.
Our DNA is a code consisting of 4 letters: A, G, C, T. These letters produce myriads of proteins that are the building blocks of life. Nature uses a minimalistic approach is it’s code which leads to higher and higher complexity in the bottom up approach of building live creatures.
The majority of scientists believed that when we decode the human DNA we would have in our disposition all the necessary guidelines to treat genetic diseases!
Then came the first surprize… It was believed that organisms with higher complexity (e.g. human population) should have greater number of genes. In fact we have the same number of genes as mice: About 30.000. There are insects that have larger pool of genes.
The second surprize that came about is that it is not all about genes. The code is not linear. Is it the interaction of genes with molecular and geometrical switches that turn on and off the genes that leads to the expression of the genome.
We realized that the phenotype (the results of genes expression) is much more complex than the sole expression of genes. Genes are turned on and off with analogy to environment pressure and this leads to the same phenotype.
Result: Two organisms with exactly the same genome will express different phenotype in different environment. It has already been seen in monozygote (with exactly the same DNA) twins.
Some scientists expected that this would happen. Zygote, which is the ovary with the DNA of the spermatocyte, contains all the necessary information to build an organism. Every cell in the zygote has exactly the same DNA. But cells differentiate to give the tissues. Necessary genes are switched on during this procedure and others are turned off. There has to be switches.
Moreover, genetic diseases with the same depletion of a part of a chromosome lead to different manifestations of the disease. This means that some genes have to be regulated accordingly for this to happen.
Epigenetics (from the greek work epi- that means above) is the new science that studies the complex mechanisms of genes being turned on and off according to environmental ques. Genome is very stable. Mutations are seldom. On the other hand the environment is very volatile. In order for the species to survive the genome has mechanisms that respond to the volatile environment by turning on and off genes.
The way genes are regulated is not well understood. Methylation of same letters of a gene is one possible mechanism. Other possibility is a specific mechanical interaction between DNA and it’s interwinding proteins, histones. Heavy research is concentrated on how epigenetics work.
There are also indications that epigenetic changes are inherited to the ancestors. This is a radical change of our frame of mind. Our lifestyle and how the environment (or our choices, e.g. smoking) affects our genes, will be inherited to our ancestors!
Epigenetics should play crucial role in the manifestation of cancer and experiemental trials are already successful in MDS ( a type of cancer).
See the paper below:
http://www.springerlink.com/content/u1340265041755rm/
If you wish to learn more about epigenetics research, see papers in the journal Epigenetics below:
http://www.landesbioscience.com/journals/epigenetics/
or for more info on epigenetics on other journals:
Groth A., et al. 2007. Science 318(5858):1928-1931
T. W. Bredy & M. Barad (2008) Learn Mem 15(1):39-45
Kertesz M. et al. 2007. Nat Genet 39:1278-84
For a more popular science approach to epigenetics see wikipedia article on it.
L.A.>
