Junk DNA?

[Anima Aeterna]

I'm somewhat skeptical if this is the right section for this sort of question or if I should post it in the Biology section but anyhow, I'd like to know more about this "Junk" DNA, and what little is known about it. I mean, most DNA being useless? Doesn't it sound silly?

 

They mention 98% of DNA is considered Junk DNA: here

 

98% is astounding. It reminds me of the myth that says we only use 10% of our brain or so, and also of a documentary I watched about how we could be as strong as a bodybuilder in emergency situations due to emergency energy stored in our muscles, etc.

 

Because it makes me think, what other amazing secrets does our body hide?

 

So anyway, feedback about this Junk DNA please. Is still very little known?

[Moontanman]

Some creatures have more junk DNA than others, an amoeba has not only more genes than a human but lots more junk DNA and a pufferfish has no junk DNA. I think the jury is still out as to whether or not junk DNA is useless....

[Anima Aeterna]

Mmh, wow, very interesting! A pufferfish is an animal with a settled course of life. He knows what he must eat, where he must go, what must he run from, etc.

 

Now Amoebas, were given their name derived from the Greek word amoibè, which means "change". So, not knowing too much about amoebas, the name seems to imply they can change their roles a lot and be very varied? So, maybe this "Junk DNA", is just DNA that doesn't have a settled function yet, but is open to receiving new functions?

 

Like for example, do professional Box players suffer DNA changes when the bones in their knuckles become stronger through training? After all, DNA does dictate our physical characteristics, right?

 

Just a thought.

[CharonY]

Junk-DNA as whole are certainly not useless. A number of these have been associated with certain regulatory functions, for instance. Also note that the amount of junk-DNA is lower than in humans, but certainly not zero. And finally, it also depends on what is lumped together in the term junk DNA in the first place.

[imatfaal]

from the perspective that I study (the law) junk-DNA has changed a bit.

 

when "DNA-fingerprinting" and databasing of genetic profiles was first mooted - it was thought that the areas of the genome that would be tested, the markers, were in junk-DNA sections. It was said that whilst these sections did provide the diversity to make the tests sound, that they did not encode for any phenotype variation - ie what was in these sections of code did not affect the characteristics, development, physique of the person. this was reassuring - and the term genetic fingerprinting added to that feeling; DNA profiles were as useful at identifying as fingerprints, and also carried little extra ethical baggage because they imparted no extra knowledge.

 

Well, now it is known that this is untrue - and whilst they may not be straightforward coding sequences they do allow us to tell much about the person's family, race, build, characteristics and disease profile. Whether this is a good thing we can leave for the ethics forum.

 

Like for example, do professional Box players suffer DNA changes when the bones in their knuckles become stronger through training? After all, DNA does dictate our physical characteristics, right?

This is completely false. You can look up Lamarckism and read about it. We pass on DNA to our children - the only genetic difference between the DNA that we receive from our parents to the section that we pass to our children is random mutation. There is epigenetics which does deal in the possiblities of passing on acquired traits to progeny - but this is a very small effect and can only be properly understood after establishing a base in normal genetics

[Greippi]

Argh. Yes. Junk DNA is a pretty outdated term (non-coding is better I suppose). While much of DNA is not contained within expressed genes, it still has an important function! As CharonY touched on, it has regulatory and spacing functions amongst other things.

[Anima Aeterna]

@imatfaal So basically, much of this "junk DNA" does actually have known "functions" and even if some are still unclear, they do have a specific coding which allows us to discover a lot of things about an individual, such as the ones you mentioned, am I right? Fascinating! I had never heard of this Lamarckism theory, I too thought about this chance that, part of the skills we acquire during our lifetime were passed on to our descendants. I thought this was the case as I was of the belief living beings evolved according to their needs. Their environment. But that was because my understanding of the DNA system was even dimmer then.

 

"Random Mutations" is a theory which still leaves me a bit skeptical, maybe in the future we'll be able to dig deeper into that as well. I think It's actually a bit more complex than the term used to refer to it isn't it? "Random mutations"? I suppose I'm too unexperienced in the area to have anything to say about it. Either way thank you very much for your explanation, I learned quite a few things just from one reply!

 

 

Thank you also to everyone else who replied thus far, sorry If I didn't mention my gratitude previously. I have a question, though. I couldn't find anything through Google about these "regulatory and spacing functions", which this non-coding DNA was believed to have. Could anyone please elaborate?

[imatfaal]

@imatfaal So basically, much of this "junk DNA" does actually have known "functions" and even if some are still unclear, they do have a specific coding which allows us to discover a lot of things about an individual, such as the ones you mentioned, am I right?

I wasn't clear. It doesn't have coding functions, or even any functions that we know of - But, it does tell us a lot about the phenotype of the individual

 

Fascinating! I had never heard of this Lamarckism theory, I too thought about this chance that, part of the skills we acquire during our lifetime were passed on to our descendants. I thought this was the case as I was of the belief living beings evolved according to their needs. Their environment. But that was because my understanding of the DNA system was even dimmer then.

Lamarckism is discredited and not correct - just in case you are still wondering!

 

"Random Mutations" is a theory which still leaves me a bit skeptical, maybe in the future we'll be able to dig deeper into that as well. I think It's actually a bit more complex than the term used to refer to it isn't it? "Random mutations"? I suppose I'm too unexperienced in the area to have anything to say about it. Either way thank you very much for your explanation, I learned quite a few things just from one reply!

No - it is just random mutations - incredible but true; there is no guiding hand or design, it is random mutations which provide a breeding advantage or disadvantage.

 

Thank you also to everyone else who replied thus far, sorry If I didn't mention my gratitude previously. I have a question, though. I couldn't find anything through Google about these "regulatory and spacing functions", which this non-coding DNA was believed to have. Could anyone please elaborate?

http://en.wikipedia..../Non-coding_DNA - I think this wikipedia page should have some interesting information on it.

 

But perhaps before diving into a sub-set of the subject get nicely up to speed on the theory and the mechanics

http://en.wikipedia....on_to_evolution

http://en.wikipedia....ion_to_genetics

[CharonY]

Note that if we use the term "junk-DNA" for all non-coding regions, it would also include regions with well-known functions. Examples include ribosome binding sites, promoters, operators etc.

On a point that Greippi touched on, the three-dimensional arrangement of DNA also influences the and rate with which for instance coding-regions are transcribed. One simple example are enhancers. In this case regulatory elements initiate a kind of loop or fold in the DNA that allows the polymerase to bind more efficiently and hence, increases transcription initiation. This effect is dependent on the distance and geometry of the loop, which, in turn, can be controlled by the length of the sequences between the enhancer and the promoter region.

 

Then there is the condensation of chromosomes (i.e. euchchromatin and heterochromatin dynamics) that is affected by length and much much more. The DNA molecule is actually highly dynamic and non-coding sequences are highly involved in that.

[Anima Aeterna]

@imatfaal Thank you! You're right, I need to know more basic information related to this topic in order to understand all of this better. Guess I got a bit carried away!

 

Thanks again to all, It's much more clear now what this "junk DNA" is about.

[Anders Hoveland]

One of the purposes of junk DNA may be to store genetic mutations from the past that are currently uncompetitive, but may be useful in the future. For example, penguins descended from ancestors with the capability of flight. Several genes potentially advantageous to the ability to fly could possibly be stored in the species junk DNA. At some point in the future if the environmental conditions change, penguins theoretically have the capability to revert back to flight through natural selection much faster, because their distant ancestors had already evolved the necessary genes.