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Childhood Stress Leaves Genetic Scars
sciencehabit writes "Traumatic experiences in early life can leave emotional scars. But a new study suggests that violence in childhood may leave a genetic mark as well. Researchers have found that children who are physically abused and bullied tend to have shorter telomeres — structures at the tips of chromosomes whose shrinkage has been linked to aging and disease."
A study (http://www.pnas.org/content/109/17/6490.full) was published in PNAS today showing how low-ranking monkeys have worse immune systems than high-ranking monkeys. (In monkey societies, 'high-ranking' is a euphemism for bully.) We've known for a long time that subordinate monkeys have worse health and live shorter lives in general than dominant monkeys, but this is one of the first studies that describe how this actually happens, genetically and physiologically.
Actually, if you RTFA you would know that the measurement only applied to two or more kinds of violence exposure. Thus, the occasional spanking without other forms of violence would not qualify as harmful under this study.
Even as recently as 2006 a majority of people still think it's acceptable to hit infants, so while some progress has been made it's hardly a solved problem.
An infant doesn't differentiate between subtle difference in forms of caretaker aggression. Since parents usually start hitting their children around the age of 12 months and this is time period is more important in terms of long-term brain development that's what I was talking about. An older child processes it differently but by the time they reach that age it doesn't really matter because the long term damage has largely already been done.
The ideal therapy would involve determining the probability of a dangerous mutation then resizing all the telomeres accordingly. You don't want excessively long telomeres (it's an intentional self-destruct mechanism for preventing a cell damaged over time from becoming malignant) just as you don't want telomeres being too short.
Cancer cells are not necessarily ones with over-long telomeres - typically what happens is that the cell's mechanism for shortening the telomeres breaks so that the cell can replicate forever. That doesn't, however, mean that it will or that the replication will occur in a timeframe that's of any significance. You'd have to have additional damage to cell mechanisms for that. If you can modify telomere length on-the-fly, the easiest one is to shorten all the telomeres in a person to something that'll only allow a few copies, then close to the deadline lengthen them just a little. That way, if a cell goes nuts and replicates excessively prior to the telomere system breaking, it'll suicide before it reaches the point of being able to replicate forever.
A better option, though considerably further into the future, would be to modify the repair mechanism in DNA to be rather more reliable. The better-able DNA is at fixing damage, the longer you can make the telomeres without it causing harm. As it stands, the mechanism has limited value. So much so that mtDNA has no such mechanism at all and can handle such a state just fine.
Of course, it helps that mitochondrial DNA is much shorter. The current nucleic DNA is a combination of the original nucleic DNA plus a lot of DNA from symbiotic organisms that became part of the cell and eventually became part of the nucleus, PLUS a great many retroviruses. Perhaps 8-10% of nucleic DNA is from fossil viruses (some still active) and according to recent studies perhaps another 40% is from other external sources.
It aught to be possible to take a fully-sequenced (and I MEAN fully-sequenced) human genome and optimize it. There'll be plenty of genes that belong to fossil lifeforms that serve no useful purpose as far as the human host and the microflora within the host are concerned. (That's over 5,500 lifeforms, so you've got to be very sure of these things.) Decrufting and compacting the human genome would likely reduce the risk of dangerous mutations. It may be that replacing the central DNA core with an XNA core would also help, but I saw nothing in that article about whether XNA molecules have the capacity to unwind properly and replicate, only that XNA had been constructed and was able to carry the same base pairs. This solution is in the FAR future (Star Trek timeframe at best) but there's nothing there that breaks any known rule. We can already do some of the steps, the main reason I'm putting it 500+ years in the future is that the problem space grows exponentially with the number of genes and even quantum computers aren't going to have sufficient power to handle a space that large for a very very long time. If ever. GM is unpredictable enough when adding/deleting single genes, but compacting DNA would involve wholesale rewrites of the genetic code.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
It used to be taught that environmental factors during an organism's lifetime (malnutrition, etc.) did not have an effect on the genetic heritage of offspring (you get a "clean slate" of DNA, so to speak). [...] But here we are with a study that says environmental factors can leave a genetic mark.
The study was about somatic cells, eg "body cells" that make up the specialized tissues of your body. Your offspring are formed from germ cells, found in your gonads, and consequently your offspring can only inherit DNA from your germ cells, but never your somatic cells (except in the case of cloning or other artificial techniques).
Telomeres are the "endcaps" of chromosomal DNA. Every time a chromosome is copied, a small portion at the ends of the chromosome get "left off" of the copy, which limits the number of time a cell can divide before the telomeres are consumed and functional DNA segments begin to be deleted. This (usually) prevents cells from reproducing in an uncontrolled fashion, and it's one of your body's main defenses against cancer. That's how it works in somatic cells.
Germ cells, on the other hand, can express a ribozyme called "telomerase," which can bind to the ends of a chromosome and extend the telomeres. This is why animals can reproduce indefinitely even though 99% of their cells are "mortal." (As others have pointed out, when a somatic cell begins to express telomerase it's usually cancer.)
The upshot of all of this is that shortened telomeres in your somatic cells will have no direct effect on your offspring. This particular study in no way supports the idea that environmental factors are responsible for genetic changes in offspring. Your post is therefore ill-informed even if your thesis is correct ("almost everything they teach in American public school is either wrong or simplified to the point of uselessness?").
To rectify your error, your homework assignment for tonight is to study the enzymes called "telomerase" and "reverse transcriptase," followed by learning the "central dogma of biology."
Dismissed.
Mama Bear: To those parents that are completely anti-spanking... hey, good luck with that. Technically, a timeout is a short period of solitary confinement, which itself deemed torture, cruel, and unusual... So before you go overboard and compare a measured spanking to beating a child... just remember, you still torture them with solitary confinement, so what makes you parent of the year, eh? ;) I'm sure a few of these velvet glovers will turn out wonderful kids. I'm also sure they will put their child so high on a pedestal to scar their unique little snowflakes in worse ways.
Papa Bear: On the other hand, if a parent ever has to hit, leave a mark, turn something red, or use something other than the palm of their own hand, they're going to far. To that kind of parent: You are bigger, stronger, and in control. For you to use a hanger, belt, stick, wooden spoon, knuckes or other hard part of the body, or anything else on a child is abuse! You're beating your child to quench your anger, not teach a lesson.
Baby Bear: Appropriate measure and balance. My son will be 4 this summer. I'm adamant about teaching him not to grab from the counter, but let's say he goes to grab a knife. I will slap the back of his hand or his bottom (after taking the knife from him calmly, of course). This isn't time to "negotiate". My son permanently injuring himself will receive a swift sting somewhere. He's a small child. He's smart, but appealing to his intellect is completely wrong when it comes to immediate danger. He doesn't run into traffic in a parking lot. He doesn't grab at the stove. He doesn't put coins in his mouth. The key is being consistent, and rare. I think the more you spank, and the harder you spank, work against you. I don't want my child resenting me, or thinking I'm out to hurt him. If he does, then I've failed. But if he gets hit by a car, I've definitely failed!
Very rarely do I ever have to spank for another reason, and that's usually if he refuses to stand in timeout. It's measured, not harsh (I am rougher when he and I are rough housing and playing... so its more embarrassing than anything), and I give him lots of warnings. If I say what the consequence will be, I always follow up. Parents that threaten punishment, and don't follow through do their kids a huge injustice just as if they continually promised ice cream for dessert, and never deliver on that either. Parents that punish without explanation are causing more problems than if they did nothing.
Any form of punishment is followed by having him explain what he did that caused the punishment ("I got a time out because I didn't listen when you told me to put up my toys."), followed by me adding explanations for why what he did was wrong, followed by a big hug, wiping of any tears, a kiss on the cheek, and telling him to go up to anyone he was bad to and apologize.
My son, is healthy, happy, knows he's loved, and is a very sweet and polite boy. He's not mean to animals or other kids. Most of the time, I've found talking quietly and firmly to my son ends all that tantrum business while shopping.
I8-D