epigenetics

Epigenetics revolution 

Introduction  

Today we are learning the language in which God created life. → unfortunately, these statements have proved at best premature. The reality is rather different.   

DNA as if it’s a template, like mold for car part in a factory. Molten metal or plastic gets poured into the mold thousands of times and out pop thousands of identical car parts→ but it’s more like script. → both productions used Shakespeare’s script, yet the two movies are entirely different → identical starting points, different outcomes. → that’s what happens when cells read the genetic code that’s in DNA. → the same script can result in different productions.  

Dutch Hunger Winter lasted from the start of November 1944 to the late spring of 1945.  

Early pregnancy 3 months during that terrible period → normal weight→ higher obesity  rates and other mental illnesses.→ some of these effect in the grandchildren  

Last 3 months of pregnancy  → born small→ stayed small 

2nd case→ Schizophrenia →1% of population→ fifty million people alive today→ one of a pair of identical twins has schizophrenia,  the other of a pair of identical twin get a chance 50% of schizophrenia. → why not 100%→ variations in 숟 environment are unlikely to account for this,  

3rd case → small child, less than 3 year old, is abuse and neglected by his or her parents. →substantially higher risk of adult mental health problems.  

These are epigenetic examples→ epigenetics can be defined as the set of modifications to our genetic material that change the ways genes are switched on or off, but which don’t alter the genes themselves.   

Or whenever two genetically identical individuals are non-identical in some way we can measure, this is called epigenetics. → when a change in environment has biological consequences that last long after the event itself has vanished into distant memory, we are seeing an epigenetic effect in action.  

Epi → at on to upon over or beside. 

Why we can’t make a baby form two sperm or two eggs, but have to have one of each. What makes cloning possible? Why is cloning so difficult? Why do some plants need a period of cold before they can flower? Since queen bees and worker bees are genetically identical, why are they completely different in form and function. why are all tortoiseshell cats female why is it that humans contain trillions of cells in hundreds of complex organs and microscopic worms contain about a thousand cells and only rudimentary organs but we and the worm have the same number of genes? 

Epigenetics is implicated in diseases from schizophrenia to rheumatoid arthritis, and from cancer to chronic pain.  

In biology, Darwin and Mendel came to define the 19소 century as the era of evolution and genetics; Watson and Crick defined the 20소 century as the era of DNA, and the functional understanding  of how genetics and evolution interact. But in the 21st century it is the new scientific discipline of epigenetics that is unravelling so much of what we took as dogma and rebuilding it in an infinitely more varied more complex and even more beautiful fashion.  

Chapter 1: An Ugly Toad and Elegant Man  

Humans are composed of about 50-70 trillion cells. → kidneys don’t start growing out of the top of our heads and there are no teeth in our eyeballs.  

Zygote → forms when one sperm merges with one egg.  Starter cell → splits in two those two ells divide gin and so on. → as they divide the cells become increasingly different from one another and form specialized cell types. → this process is known as differentiation. → the cells have become completely different even though they came from one cell with just one blueprint.  

What’s much more interesting is the exploration of how cells use the same genetic information in different ways. Perhaps even more important is how the cells remember and keep on doing it. → cells in our bone marrow keep on producing blood cells, cells in our liver keep on producing liver cells. Why does this happen? 

One possible and very attractive explanation is that as cells become more specialized they rearrange their genetic material, possibly losing genes they don’t require.  

Liver is vital and extremely complicated organ. 500 functions. But gets rid of the hemoglobin gene, which it simply never uses. 

As they differentiate, cells could jettison hundreds of genes they no longer need. There could of course be a slightly less drastic variation on this → maybe the cells shut down genes they aren’t using. → loss of genes or irreversible inactivation. 

Turning back the biological clock 

Gurdon → the way he did this was to take a nucleus from the cell of an adult toad and insert it into an unfertilized egg that had had its own nucleus removed. (somatic cell nuclear transfer (SCNT) → the experiments were designed to test the following hypothesis: as cells become more specialized(differentiated) they undergo an irreversible loss/inactivation of genetic material. There were two possible outcomes to these experiments: 

John Gurdon spent around fifteen years, starting in the late 1950s, demonstrating that in fact nuclei from specialized cells are able to create whole animals if place in the right environment ie. An unfertilized egg. → epigenetic is the something in these cells. The epigenetic system controls how the genes in DNA are used, in some cases for hundreds of cell division cycles, and the effects are inherited from when cells divide.  

The epigenetic landscape  

Conrad Waddington epigenetic landscape→ the ball at the top of the hill is the zygote, as the various cells of the body begin to differentiate , each cell is like a ball that has rolled further down the hill and headed into one of the troughs.  

John Gurdon → cloning the recreation of an animal from the cells of an adult- is possible. 2nd → cloning is really difficult, because he had to perform hundreds of SCNTs for every toad that he managed to generate.  

Dolly 1996  → first why is cloning animals so inefficient, second,  why are the animals so often less healthy than natural offspring?→ the answer in both cases is epigenetics.