Epigenetics : Overview of a hidden story

Fate beyond DNA...............

Human genome promised initially to be a magic bullet against all human afflictions. Soon it appeared to be more complex than ever imagined.

There is something more than genes what we inherit. An overlaying code called the epigenome is being unravel led  with startling new findings each day. There was a time, not so long ago when everybody though that deciphering of human genome would bridge in the gap in our knowledge between genes and  human disorders. It was immediately conceived  that the results and its further mining could be  magic bullet against most of human disorders .  But nature  puzzled  us once again.

Layer of coding over the existing genome, which was primarily responsible for its expression and regulation, was unraveled.

Its not difficult to envisage  the impact of epigenetics. For example In all of the nearly 274 types of cells in our body, each one of it contains the same human genome yet they are so different in their physiological structure and function. What stops the heart cell from making insulin  secreting  pancreatic cells ? Or why do certain genes are active in one stage of developmental pathway stops its production in other?

All of these secrets are being demystified in the light of epigentics.

Subtle chemical changes in DNA can remarkably effect its exposure to transcriptional machinery. DNA is tightly bound to histone proteins in nucleosome. So its evident, If we visualize the structure three dimensionally,  one thing fairly east to understand is, more loosely a  DNA is bound in nucleosome,   its access by the transcriptional machinery would be more easy.

For example, Acetylation of certain histones create electrostatic repulsion between the negatively charged DNA and acetyl group on other-wise positively charged histone proteins. Creating space for transcriptional player to act upon.

Another way could be to chemically modify DNA with certain molecules so that transcriptional machinery doesn’t roll over it easily. Here too nature has a plan. Methylation of certain cytosine residues on the DNA suppresses the expression of those particular gene segments..........

(more to come ..)