(Q for Theist) Why didn't "God" give Cetaceans gills?
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23-02-2014, 05:28 PM
RE: (Q for Theist) Why didn't "God" give Cetaceans gills?
(23-02-2014 04:18 PM)Raptor Jesus Wrote:  
(23-02-2014 03:36 PM)Momsurroundedbyboys Wrote:  I was watching a show (somewhere, honestly don't recall when, where, what or why) and they mentioned junk DNA and how they isolated that DNA and removed it or soemthing from mice and the mice were completely "normal" which I guess it confirmed the fact junk DNA is just there and has no purpose.

Then they went on to mention that blowfish have no junk DNA. I found it odd...

Is junk DNA just mutations that are meaningless? How did a blowfish end up with none?
That’s a good question. I haven’t heard of the blowfish having no “junk” DNA. I’ll look into it and see what I can find out. Sounds interesting, whatever it actually is.

There is some disagreement on whether “junk” DNA is actually junk. Or at least whether all of it is junk. The argument is basically, some of it might serve some indirect purpose that we just don’t know yet. I haven’t really been following the details of that argument, that it does something indirectly, so I don’t know how that would even work if true.

But either way, there is definitely DNA that seems to do nothing, and a LOT of it. We are loaded with the stuff. One thing I’d add to what Revenant77x said on that is that some of the genes for gills are still used in part to form our jaws, and inner ear bones, with added mutations to make those adaptations work. But Revenant77x is as correct, there are genes that served purposes in ancestral species, like some of our gill genes, that underwent mutations that rendered them nonfunctional, by damaging the gene or by mutations that did not effect that “physical” gene directly, but prevented the expression of that gene.

For example, whales have genes for teeth, and began developing them in embryotic development, but then stop and the teeth go away. We produce three different sets of kidneys in utero, but only keep one set. The first set we develop are fish kidneys, but never function, even in the womb, and are reabsorbed during our development. So some of the genes are active at some point, but suppressed or not continued to develop, at another point, and never serves a purpose in the birthed organism, or in utero. Geese have genes for teeth, for example, and in very rare circumstances some geese are born with teeth. The gene to prevent the expression of that gene, in that case, was not present or was blocked by some other gene.

There are loads of examples like this, which we expect to find due to having previous morphology in our ancestry. That’s why some of our “junk” is there, because we have very long histories of evolution that extends far past our own species. That accounts for a lot of it. But in a number of cases they are just chance mutations, that fail to code for any protein production at all (which is all DNA does anyway, code for protein production), so if a mutation occurs that does not produce a protein, then there is no effect on the organism, other than extra DNA in the genome. Without the mutation creating new, or varied amounts, of proteins, then it has no effect on the physiology of the organism, so natural selection has no way to work on it, either positively or negatively. So unless it is randomly mutated away (in which case it would still probably just mutate into a different form of “junk” DNA), it just sits there and continues to be replicated, as long as it’s “lucky” enough to have mutated into an origins that is successful in reproducing itself.

Given time, with chance creating them, and nothing selecting against them, this “junk” non-protein coding DNA can build up over time. The more time, the more mutations can happen, and given billions of years, you can end up with a lot of it. DNA doesn’t “care” about what they “do” for the organism. Just that it reproduces.

Because of this, like Revenant77x said, I too find it highly unlikely that a blowfish would have no “junk” DNA. There would have to be a process by which it were removed, and I can’t think of what that process could possibly be, if it’s not even expressing itself in the form of changing the organism, or the cells in which the DNA resides, for it to be selected against.

Yeah I meant the gill thing as a quick and dirty example for clarity rather than 100% accuracy. Some people can't ever let that kind of thing go. Of course Junk DNA is only useless as far as we can tell, it might be doing things we just don't know about yet.

(31-07-2014 04:37 PM)Luminon Wrote:  America is full of guns, but they're useless, because nobody has the courage to shoot an IRS agent in self-defense
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24-02-2014, 12:17 AM
RE: (Q for Theist) Why didn't "God" give Cetaceans gills?
(23-02-2014 05:09 PM)Momsurroundedbyboys Wrote:  Thanks for your reply. I appreciate it a lot. I did a rather quick search in google and found that the pufferfish (or blowfish -- guess it's kinda like calling a pill bug or roley poley Big Grin ) does have some junk DNA but no where what it was believed to have had -- or maybe what they thought it should have...I dunno. It seems some wonder if the pufferfish might have a way of just acquiring 'junk' DNA or removing genes that haven't a purpose.

I tried to read more about it, but became bored -- which I know speaks more about me than the writers. One article was penned by PZ Meyers in some science website. That article (labeled "intermediate") was way over my head. Weeping This is why even if it's interesting to me, I stop because I just end up feeling stupid.

I think I'm going to search for an article about the removing "junk" DNA from mice.

Okay, so only 3% of the human genome contains functional coding DNA. The roughly 97% left of it is "junk" DNA.

I looked into articles on the puffer fish genome. They say the puffer has 15% coding DNA, compared to our 3%. But that's not because it has more genes. It apparently has about the same number of genes as humans, some where around 23 thousand or so genes. It's just that the human genome houses so much "junk" DNA that it's 7.5 times larger than that of the puffer genome. So the puffer still has a large amount of "junk". Roughly 85% of it's genome is.

Nothing I've read so far states anything unusual about this. It just seems scientist like to study the puffer fish genome because it is so much smaller, and has such a lower percent of "junk" in it. This makes it easier and quicker to read through it all as there is less nonsense DNA to read though, attempt to figure out, and account for. It's like if you were trying to decode 750 pages of code in which only 3% even says anything, vs trying to decode 100 pages of code, with 15% of it meaning something. Plus, a lot of those genes in puffer fish are shared in the human genome, as we have common ancestry in fish. Scientist prefer to work with the puffer genome, because they can more quickly identify genes in the sequence, decode them, and then apply that information to locate those same genes in human's by finding their matches in the human genome if they are shared.

Nothing I read said why there was less "junk" in puffers, but it seems likely that it's simply because some species will, by chance, have more, and other species less. Scientist just found and utilized one of the species that had less, but still shares significant enough common ancestry to be useful.

I also read a couple things that seem to imply some minor indirect aspects of junk DNA that can be useful. Though still non-coding DNA, it helps put space between active genes. That space seems to help prevent destruction of functional genes by various types of genetic mutations caused by insertions, deletions, frameshifts, etc. It simply decreases the risk of a random mutation happening at a location that lies on an active gene. Only 3% chance in humans, 15% chance in puffers, for example. If you consider what having no "junk" DNA would mean would be that 100% of the genome would be functional genes. So every time an insertion, deletion, etc..., event happened it would happen to functional genes. In that sense the "junk" DNA's presence may help protect genes from too many mutations.

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24-02-2014, 12:26 AM
RE: (Q for Theist) Why didn't "God" give Cetaceans gills?
(23-02-2014 05:09 PM)Momsurroundedbyboys Wrote:  ... I did a rather quick search in google and found that the pufferfish (or blowfish -- guess it's kinda like calling a pill bug or roley poley Big Grin )...

Oh and by the way, I tend to use pufferfish and blowfish interchangeably. Smile

There are also boxfish and cowfish. They are all basically the same thing. Box and cow fish are types of pufferfish. I have a puffer in my aquarium. It's why I know.

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24-02-2014, 12:44 AM
RE: (Q for Theist) Why didn't "God" give Cetaceans gills?
Thanks Raptor Jesus! I really do appreciate you taking the time to explain this.


God is a concept by which we measure our pain -- John Lennon

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24-02-2014, 12:52 AM
RE: (Q for Theist) Why didn't "God" give Cetaceans gills?
No problem. I find it all interesting anyway. And I didn’t know that particular thing about them using the puffer genome in this way before, so thank you for asking!

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