http://www.hopkinsmedicine.org/press/2002/November/epigenetics.htm
Epigenetics and Imprinted Genes

There is far more to genetics than the sequence of building blocks in the DNA molecules that make up our genes and chromosomes. The
"more" is known as epigenetics.

What is epigenetics?
Epigenetics, literally "on" genes, refers to all modifications to genes other than changes in the DNA sequence itself. Epigenetic
modifications include addition of molecules, like methyl groups, to the DNA backbone. Adding these groups changes the appearance and
structure of DNA, altering how a gene can interact with important interpreting (transcribing) molecules in the cell's nucleus.

How do epigenetic modifications affect genes?
Genes carry the blueprints to make proteins in the cell. The DNA sequence of a gene is transcribed into RNA, which is then
translated into the sequence of a protein. Every cell in the body has the same genetic information; what makes cells, tissues and
organs different is that different sets of genes are turned on or expressed.

Because they change how genes can interact with the cell's transcribing machinery, epigenetic modifications, or "marks," generally
turn genes on or off, allowing or preventing the gene from being used to make a protein. On the other hand, mutations and bigger
changes in the DNA sequence (like insertions or deletions) change not only the sequence of the DNA and RNA, but may affect the
sequence of the protein as well. (Mutations in the sequence can prevent a gene from being recognized, amounting to its being turned
off, but only if the mutations affect specific regions of the DNA.)

Yes, epigenetics is facinating. Some people did a study [denmark i think]
that traced family trees, and found a connection in the grandchildren of
women, where the women suffered malnutrition during famine periods, and it
was consistent. IOW the effects skipped an entire generation and was
consitent. They found that it was the "epigentics" of genes that affected
later generations, and not eh DNA/chromosomes themselves. they had very
detailed records in that country [ not a common thing in others ] that
enabled them to track this info back over 100 years.

Anyway, a side line is that general science studies are often restricted by
what historical records are accessible, and not the "theory" itself, so that
it becomes a matter of never enough proof to show a caustive link in some
scientists thinking. ... it's a slow process, and always unfolding.

sorry don;t have link handy.
"Sir Frederick" fuzzysys.com> wrote in message
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