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Добра статия-синтез относно епигенетиката. Копирам и не по-малко интересните коментари под нея.
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In simplified terms, (the study of heritable changes in phenotype that does not involve changes in the underlying DNA sequence) is the study of biological mechanisms that will switch genes on and off. What does that mean? Well, if you are new to this whole thing, we first need a quick crash course in biochemistry and genetics:
- Cells are fundamental working units of every human being. All the instructions required to direct their activities are contained within the chemical deoxyribonucleic acid, also known as DNA.
- DNA from humans is made up of approximately 3 billion nucleotide bases. There are four fundamental types of bases that comprise DNA – adenine, cytosine, guanine, and thymine, commonly abbreviated as A, C, G, and T, respectively.
- The sequence, or the order, of the bases is what determines our life instructions. Interestingly enough, our DNA sequence is mostly similar to that of a chimpanzee. Only a fraction of distinctively different sequences makes us human.
- Within the 3 billion bases, there are about 20,000+ genes. Genes are specific sequences of bases that provide instructions on how to make important proteins – complex molecules that trigger various biological actions to carry out life functions.
Now that you understand genetics, let’s learn about epigenetics. Epigenetics, essentially, affects how genes are read by cells, and subsequently how they produce proteins. Here are a few important points about epigenetics:
- Epigenetics Controls Genes. Certain circumstances in life can cause genes to be silenced or expressed over time. In other words, they can be turned off (becoming dormant) or turned on (becoming active).
- Epigenetics Is Everywhere. What you eat, where you live, who you interact with, when you sleep, how you exercise, even aging – all of these can eventually cause chemical modifications around the genes that will turn those genes on or off over time. Additionally, in certain diseases such as cancer or Alzheimer’s, various genes will be switched into the opposite state, away from the normal/healthy state.
- Epigenetics Makes Us Unique. Even though we are all human, why do some of us have blonde hair or darker skin? Why do some of us hate the taste of mushrooms or eggplants? Why are some of us more sociable than others? The different combinations of genes that are turned on or off is what makes each one of us unique. Furthermore, there have been indications that some epigenetic changes can be inherited.
- Epigenetics Is Reversible. With 20,000+ genes, what will be the result of the different combinations of genes being turned on or off? The possible permutations are enormous! But if we could map every single cause and effect of the different combinations, and if we could reverse the gene’s state to keep the good while eliminating the bad… then we could theoretically* cure cancer, slow aging, stop obesity, and so much more.
Here’s an analogy that might further help you to understand epigenetics. Think of the human life span as a very long movie. The cells would be the actors and actresses, essential units that make up the movie. DNA, in turn, would be the script — instructions for all the participants of the movie to perform their roles. Subsequently, the DNA sequence would be the words on the script, and certain blocks of these words that instruct key actions or events to take place would be the genes. The concept of genetics would be like screenwriting. Follow the analogy so far? Good. The concept of epigenetics, then, would be like directing. The script can be the same, but the director can choose to eliminate certain scenes or dialogue, altering the movie for better or worse. After all, Steven Spielberg’s finished product would be drastically different than Woody Allen’s for the same movie script, wouldn’t it?
* Editor’s Note: Be wary of self-help claims that exploit epigenetics and seem too good to be true. We recommend you read about the abuse of .
Ready to learn epigenetics in further detail? Read on:
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Comments
Gary Camp • 4 months ago
It is still not at all clear to me how information can be passed on from generation to generation (like in the recent article on Heart Attacks, "Memory of a heart attack is stored in our genes"). To be passed on there must be a change to the fertilized egg (or at least the growing baby organism). How is this accomplished?
mastercytosine Mod Gary Camp • 4 months ago
Hi Gary! Glad to see your interest in epigenetics! Reproductive cells (eggs and sperm) contain intact genetic information. During the reproductive process, the epigenetic tags are erased through what is known as "reprogramming" so that they can be re-programmed into specialized cells (blood, hair, etc). However, in mammals, about 1% of genes bypass this reprogramming process and end up with epigenetic tags being passed down, also known as epigenetic imprinting! Take this with a grain of salt though as epigenetic changes rapidly occur (relatively speaking) and it is difficult to prove whether they were inherited or induced by environmental changes again.
Carl • 10 months ago
Assuming 3 billion base pairs (correct) and about 99% nucleotide base pair correspondence between chimpanzees and human beings (incorrect- it is now around 96% and it depends on the size of nucleotide strands and how they're lined up, either human to chimpanzee or chimpanzee to human, but that's another story), approximately 1% of 3 billion is 30 million (based on your numbers), so where on earth do you get 15 million base pairs that differ!? I know-you maintain less than 1%, but that is just plain false. Furthermore, utilizing the assumed correct 96% base nucleotide correspondence, the number of different bases is actually 120 million, four times more than the previous number i mentioned mentioned, and more than 10 times the difference you stated in your article. Ugh! Get your facts straight and your numbers will follow!
John Doe Carl • 22 days ago
You are the coolest person alive.
mastercytosine Mod Carl • 10 months ago
Hi Carl. Thanks for pointing these numbers out! These figures have always debated on and have frequently changed over the years. Since there are many ways to interpret the count, we have decided to edit out the actual numbers in its entirety as they serve no purpose within the context of this article to convey the point (which is that a small amount of sequences can have great impact). Thanks for reading WhatisEpigenetics.com!
John Doe mastercytosine • 22 days ago
You could just say Carl was right and you were wrong
Carl • 10 months ago
Correction-not enough trimmethylxanthine today. 8 Exactly 8 times more than the number you stated.
Carl • 10 months ago
To clarify, I'm talking about haploid, not diploid (6 billion nucleotides), because it is assumed that bases will correspond as base pairs. So my writing here wss not clear and should state "bases" rather than base pairs. Also, there is more research out there demonstrating that humans and chimpanzees do not even have the 96% base correspondence claimed, especially when the Y chromosome is examined. Do we understand more or less of the human genotype? Definitely less. No one in the field of genetics would argue that fact. Now geneticists are saying that it will take hundreds of years to map out the real correspondences and causal relationships, when functioning and non functioning DNA are taken into consideration, and when the unsearchable complexity of this amazing (euphemism) self-replicating, self regulating, self-correcting living informational system is given it's proper reverence and humility (neither come easy to human being, me included here). So easy on the "we're just like chimpanzees" except for a few Lego pieces nonsense. When a chimpanzee can fly a 747 then I'll relent in my opinion. Better yet, give a chimpanzee your tax return to complete and then send the results to the IRS! Errant nonsense!!
Редактирано от Mod vege на 06.01.17 05:28.
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Explanation of Epigenetics for Total Beginners [re: Mod vege]
(старо куче)
