Science Q&A

[thalassa]

Have a math or science-y question that you've always wondered?

I think we have enough math and sciencey people here to answer it...

Ask away!

[anunitu]

Re: Science Q&A

OK,here is a good science and biology question:Why do we age.?

[Munin-Hugin]

Re: Science Q&A

OK,here is a good science and biology question:Why do we age.?

Trust me. There are plenty of folks out there that I'm glad will age and die. There's too many of them that need to get removed from the gene pool.

[anunitu]

Re: Science Q&A

The question stands..

[Munin-Hugin]

Re: Science Q&A

In all truthfulness, I'd have to say that it's because nothing is created to exist forever. All systems do not have the capacity to deal with the rigors and stresses of the simple act of existing. Think about it as if we were using a copy machine, with our cells being the thing copied. As our bodies grow, obviously it requires more cells to make up our mass. One cell becomes two, but in splitting, there are going to be tiny flaws created by the act of multiplication. Then the flawed cells divide, and so on and so on. If you make a copy of a copy of a copy of your favorite picture, eventually it will cease to be as crisp and clear and recognizable as the original, due to the fact that microscopic imperfections just get more and more noticeable over time until it's made up of more damaged parts than whole parts.

Scar tissue is a great example of this, as while it's made up of the same stuff as the skin around it, it's a different color, texture, thickness, etc.

[anunitu]

Re: Science Q&A

Scar tissue is a different color because it is NEW skin cells against the backdrop of OLD skin cells..

[B. de Corbin]

Re: Science Q&A

Uhm... Entropy? A general trend toward disorder. The copies of themselves that our cells make generate an increase in replicator error...?

[thalassa]

Re: Science Q&A

Because the topic came up in another thread (and I'm sad that this thread is lonely):

What is epigenetics?



THE SHORT VERSION:

At its very most basic, epigenetics is describes inheritance that isn't from coding DNA...though this is a somewhat imprecise definition because coding DNA can sometimes also be non-coding DNA, depending on how the DNA is "labeled" at the time...and...it gets complicated. One of the sources

THE LONG VERSION (PART 1):
So...to answer this better, we need to talk about DNA.

I'm pretty sure, unless you are a biology geek that is really into genetics or a biologist that the model of DNA that you were taught highlighted it as a "zipper-like" molecule that twisted into a the "twisted ladder" (or double helix) shape that Rosalind Franklin discovered (see me rewriting history?). You may also have been taught that your DNA molecules were "bound up" somehow (maybe "coiled"), but basically super packed into the shapes we know as chromosomes. And there was probably something in there about how the 4 molecules that make up the "language" of DNA (A, T, C, and G) work together to "code" for different amino acids which are put together to make proteins. (What DNA looks like)

And this is all true, but it is pretty much the very most basic information about DNA--this is basically what you learn in a freshman biology class. And, unless you took your biology class in the last few years, you probably were taught that most of your DNA is "junk" or non-coding DNA that either has no purpose (worst case teacher) or has an unknown purpose (best case teacher).


But the real "basic structure" of DNA is brilliantly paradoxical. Its really (enter sappy stuff) one of the most beautiful, miraculous, and amazing things that have come to being in the universe. Its incredibly simple, incredibly complex, and allows for an almost infinately diverse set of structures to arise, but follows fairly static rules and is (in one form or another related form) in every living (and some non-living) being that we know of.

^a very basic animation of how DNA is packaged


So...what this has to do with epigenetics is that your DNA basically has a code (or series of codes) for reading the code...or maybe a filing system to know what parts of the code to read for different functions...or maybe a series of switches that makes sure the right code gets read at the right time ( or sort of all of these at the same time):

really

http://www.theguardian.com/science/occams-corner/2014/apr/25/epigenetics-beginners-guide-to-everything

Another way to think about it...

Epigenetics is sometimes compared to software operating on the hardware that is a genome. A more useful metaphor is an analogy to music, devised by Eva Jablonka and Marion Lamb in their seminal Evolution in Four Dimensions. Think of a genotype as a musical score and its phenotype as a specific performance of the score. A score can be copied and transmitted in musical notation, just as DNA is replicated. But the score is interpreted in particular performances, as DNA activity differs from cell to cell. Every performance varies, as in cell differentiation. Individual performances can influence performances by others, just as a cell's epigenetic patterns are bequeathed to daughter cells. Individual performances also can influence future generations of performers by means of recordings, just as epigenetic patterns can be passed to offspring.

http://bioscience.oxfordjournals.org/content/59/9/736.full

The importance of epigenetics comes in when we talk about cellular differentiation, and how organisms develop (we'll talk about the epigenetic implications of your grannie's environment in part 2).

Epigenetics is CRITICAL in developmental processes:

http://bioscience.oxfordjournals.org/content/59/9/736.full

I'm not sure if anyone wants to know about mechanisms of how this works or not...if so, let me know and I'll see what I can find by way of visual aids, because its an easier way of understanding what goes on.





Part 2, I'll talk more about how environmental factors affect change, why epigenetic change matters, and what we know so far about how our genomes actually change.

[thalassa]

Re: Science Q&A

The question stands..

Do you mean why do humans age, or animals/life forms in general? Corbin and Munin have part of it, but if you want to know biological mechanisms, I can talk about some of them. Not my area of expertise, but I know some of the basics of what we know.

[anunitu]

Re: Science Q&A

Mainly humans,but animals also share this,so basic stuff.

[thalassa]

Re: Science Q&A

What is epigenetics?

(Part 2)


Woah, check out what I found! And episode of NOVA I've not seen before! (scampers off to watch)

...okay...so this episode will explain the basics, AND tell you why its important, AND tell you a very limited bit about the mechanics of how it works.

Honestly, if you watch that, you'll probably know everything you need to know as a lay person!



(the first bit of this article also explains a little bit more the "big 3" ways epigenetic changes can occur)


And, some other good info:

Originally these epigenetic changes were believed to occur only during fetal development. But pioneering studies showed that molecular bric-a-brac could be added to DNA in adulthood, setting off a cascade of cellular changes resulting in cancer. Sometimes methyl groups attached to DNA thanks to changes in diet; other times, exposure to certain chemicals appeared to be the cause. Szyf showed that correcting epigenetic changes with drugs could cure certain cancers in animals.
Geneticists were especially surprised to find that epigenetic change could be passed down from parent to child, one generation after the next. A study from Randy Jirtle of Duke University showed that when female mice are fed a diet rich in methyl groups, the fur pigment of subsequent offspring is permanently altered. Without any change to DNA at all, methyl groups could be added or subtracted, and the changes were inherited much like a mutation in a gene.

source

Also, from the above article, there's something to be said for so-called "genetic memory"...its just not what the New Agers want it to be:

According to the new insights of behavioral epigenetics, traumatic experiences in our past, or in our recent ancestors’ past, leave molecular scars adhering to our DNA. Jews whose great-grandparents were chased from their Russian shtetls; Chinese whose grandparents lived through the ravages of the Cultural Revolution; young immigrants from Africa whose parents survived massacres; adults of every ethnicity who grew up with alcoholic or abusive parents — all carry with them more than just memories.

s

It works like this--environment shapes genome by determining what parts of the genome are expressed by acting as a "switch" that turns them on or off, that highlights them for other chemicals. This might come from environmental exposures--cadmium and other heavy metals, certain pesticides, tobacco smoke...or from the experience of stress--famine, depression, etc. All these types of things cause a change in body chemistry, which affects the "switches"(or triggers...depends on what you want to call it as an analogy).

These changes accumulate over time--this partially answers a small piece of your aging question Anu.....also, telomeres. They also influence eggs and sperm (which means they are passed on differently in men and women).


Scientific studies

Loving mothers matter to the genome--The importance of licking baby rats (I'm pretty sure, if this is replicated, this will become a classic experiment of biology)...also, quite a bit about stress

Epigenetics may predict ADHD-- alcohol, tobacco, medications, environmental chemicals, and psychosocial stressors trip the genetics (some studies suggest this might lead to new treatments)

There's plenty more...but I have to get kids in bed

[B. de Corbin]

Re: Science Q&A

Here's where I got my first crude intro to epigenetics:

Plastic People

I know I'll never really understand it, but it is an interesting addition/refinement to genetics/evolution/ecology, and a rough knowledge adds food to the plate of a hungry mind...

Thanks, Thalassa!