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We used to think that a new embryo's epigenome was completely erased and rebuilt from scratch. But this isn't completely true. Some epigenetic tags remain in place as genetic information passes from generation to generation, a process called epigenetic inheritance.
Epigenetic inheritance is an unconventional finding. It goes against the idea that inheritance happens only through the DNA code that passes from parent to offspring. It means that a parent's experiences, in the form of epigenetic tags, can be passed down to future generations.
As unconventional as it may be, there is little doubt that epigenetic inheritance is real. In fact, it explains some strange patterns of inheritance geneticists have been puzzling over for decades.
Most complex organisms develop from specialized reproductive cells (eggs and sperm in animals). Two reproductive cells meet, then they grow and divide to form every type of cell in the adult organism. In order for this process to occur, the epigenome must be erased through a process called "reprogramming."
Reprogramming is important because eggs and sperm develop from specialized cells with stable gene expression profiles. In other words, their genetic information is marked with epigenetic tags. Before the new organism can grow into a healthy embryo, the epigenetic tags must be erased.
At certain times during development (the timing varies among species), specialized cellular machinery scours the genome and erases its epigenetic tags in order to return the cells to a genetic "blank slate." Yet, for a small minority of genes, epigenetic tags make it through this process and pass unchanged from parent to offspring.
Proving epigenetic inheritance is not always straightforward. To provide a watertight case for epigenetic inheritance, researchers must:
Rule out the possibility of genetic changes
In organisms with larger genomes, a single mutation can hide like a needle in a haystack.
Show that the epigenetic effect can pass through enough generations to rule out the possibility of direct exposure
In a pregnant mother, three generations are directly exposed to the same environmental conditions at the same time. An epigenetic effect that continues into the 4th generation could be inherited and not due to direct exposure.
Researchers face the added challenge that epigenetic changes are transient by nature. That is, the epigenome changes more rapidly than the relatively fixed DNA code. An epigenetic change that was triggered by environmental conditions may be reversed when environmental conditions change again.
Epigenetic inheritance adds another dimension to the modern picture of evolution. The genome changes slowly, through the processes of random mutation and natural selection. It takes many generations for a genetic trait to become common in a population. The epigenome, on the other hand, can change rapidly in response to signals from the environment. And epigenetic changes can happen in many individuals at once. Through epigenetic inheritance, some of the experiences of the parents may pass to future generations. At the same time, the epigenome remains flexible as environmental conditions continue to change. Epigenetic inheritance may allow an organism to continually adjust its gene expression to fit its environment - without changing its DNA code. |
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| There are no conversations. |
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| Brian Acton |
Going public is 18-month process, while an acquisition is a 6-month process. Going public means going under so much scrutiny, regulatory approval, auditing, magnified 10 times. Having the stomach to do that isn't necessarily in my DNA. My DNA is building a product and a service. |
| Andrew Card |
The Oval Office symbolizes... the Constitution, the hopes and dreams, and I'm going to say democracy. And when you have a dress code in the Supreme Court and a dress code on the floor of the Senate, floor of the House, I think it's appropriate to have an expectation that there will be a dress code that respects the office of the President. |
| Mike Ferguson |
Very few pilots even know how to read Morse code anymore. But if a pilot could read Morse code, he could tell which beacon he was approaching by the code that was flashing from it. |
| Stephen Hawking |
Stem cell research is the key to developing cures for degenerative conditions like Parkinson's and motor neuron disease from which I and many others suffer. The fact that the cells may come from embryos is not an objection, because the embryos are going to die anyway. |
| Sebastian Faulks |
I think my generation has had an unbelievably easy time profiting from the world that was made for us by our parents and grandparents. We are essentially a rather frivolous generation. The Blair government was my generation's shot at power. It had some good things, but it had some flaws. |
| Herman Cain |
The 9-9-9 plan would resuscitate this economy because it replaces the outdated tax code that allows politicians to pick winners and losers, and to provide favors in the form of tax breaks, special exemptions and loopholes. It simplifies the code dramatically: 9% business flat tax, 9% personal flat tax, 9% sales tax. |
| Neil Gaiman |
A library is a place that is a repository of information and gives every citizen equal access to it. That includes health information. And mental health information. It's a community space. It's a place of safety, a haven from the world. |
| Geoffrey Canada |
In two-parent households, women have increasingly entered the workplace, and in single-parent households, there is even more of a need for the adults to work. That means parents do not fully control their own schedule and have to scramble to find high-quality after-school options. |
| Gilbert K. Chesterton |
The object of a New Year is not that we should have a new year. It is that we should have a new soul and a new nose; new feet, a new backbone, new ears, and new eyes. Unless a particular man made New Year resolutions, he would make no resolutions. Unless a man starts afresh about things, he will certainly do nothing effective. |
| Colin Camerer |
Charles Darwin and I and you broke off from the family tree from chimpanzees about five million years ago. They're still our closest genetic kin. We share 98.8 percent of the genes. We share more genes with them than zebras do with horses. And we're also their closest cousin. They have more genetic relation to us than to gorillas. |
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