Question about DNA

S

swetha

Registered Member
hi!
my name is swetha.I am from india.
i require some help regarding DNA.
As in, what happens to the DNA which we take in when we eat fruits vegetables or raw meat?
will all the DNA be broken down ?
is there any way tat the human cell could take up the DNA if any is remaining from the digestive tract?(similar to bacterial transformation)
i would really be glad if someone could get bac to me with some information on this.
thank you
 
Yes, all of it will be broken down to it's bases, and likely further into deoxyribose, a nitrogenous base, and a phosphate. Humans cannot take up DNA and incorporate it into their genome in the same way bacteria do, at least not from the food they ingest.
 
itsnt there even a small chance of a very small percentage of the DNA not getting degraded?
as DNA is quite stable
 
DNA is quite stable, but there is a family of enzymes called DNases that destroy DNA. These enzymes, along with their couterparts RNases, are very hardy and exist basically everywhere. After the DNase is finished it's work, there won't be any sequence of value left over.
 
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what if the DNAases havent got aroung to degrade the DNA...are thr still no possiblities?
 
DNases are everywhere, including within the cell membrane of cells. You need to be ridiculously diligent in sterilizing anything that will touch a DNA sample in order to keep it free of DNases. It is even worse with RNA. In the digestive tract, there is no escape. And our cells don't readily take up DNA and incorporate it into themselves. They have to be "coerced".

I would say there is no reasonable chance, and this idea shouldn't be considered as possible.
 
Although the stomach acids/DNAses will degrade 99% of DNA beyond recognizable genetic form, there is still a chance that some of the epithelium lining the digestive tract will be able to take up a gene of plant origin (since most meat is cooked, the chance of taking up animal DNA is next to nothing). However, only the epithelium of the digestive tract will take this DNA up and, since there will be no telomeres/centromeres indicating that this uptaken DNA is a chromosome, it will not survive a division of cells. So the chance that any uptaken DNA will be passed on to the next generation of people is less than next to nothing since:
1) All genes will likely be destroyed in the environment of the stomach
3) Almost no remaining genes will be able to pass through the extracellular material/membranes of digestive tract epithelium
3) All genes passing this point will only be expressed in those particular cells and not any daughter cells
4) Plant genes will likely not be expressed in mammalian cells (too different) - and all animal genes will likely be destroyed by the process of cooking
5) None of the digestive tract epithelium will give rise to more than 2 generations of daughter cells, let alone the germinal cells (sperm/egg) of another generation.
Therefore, any DNA that you eat has absolutely no effect (beyond say, 48 hours or so, and even that is a remote possibility) on your or your offsprings' life.
 
Actually, though, DNases are not as resilient as RNases. A standard autoclave cycle can get rid of essentially all DNases (but not so RNases).
 
And DNases are not in ANY cellular membranes (except, per se, in the process of secretion).
 
wat abt if the meat is uncooked like sushi??? Could the integrated Dna be a cause for cancer????
 
I don't believe that DNA from ingestion will be taken up and incorporated into any cells. The chances for even plant DNA are far too slight.

I suppose that if it were to happen though, then yes it could start off the chain of events leading to cancer, by interrupting the expression of a cell growth/cell division regulatory gene. This would not immediately cause cancer, but would be a starting point.

I suppose that there are no DNases inside cells, but there are nucleases and other such gene products that degrade DNA that are not classified as DNases. These would easily take care of what the DNases left behind.
 
Idle Mind said:
I suppose that there are no DNases inside cells.....
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There are lots of different types of DNases and RNases in cells! :eek: DNase and RNase are proteins that are made by cells. They play a vital role in DNA repair and RNA turnover respectively. They also play a role in cellular defenses against viral infections.

As has been stated already by a couple of posts above, it is highly unlikely that ingested DNA will be taken up by epithelial cells of the alimentary tract. Eukaryotic cells just don’t naturally take up foreign DNA like bacteria do. Even if it did happen, it is of no consequence because the tissue turnover rate of the gut is very quick. The entire epithelial lining of the small and large intestine is shed and replaced in the space of about 2 weeks.<P>

swetha said:
Could the integrated Dna be a cause for cancer????
Click to expand...

No, ingested DNA does not enter the epithelial cells and integrate for the reasons stated above. I used to work in a lab that focuses on colon cancer. The cascade of gene mutations that results in colon cancer is quite well known. It’s a very reproducible series of mutations in specific genes. If the insertion of ingested foreign DNA was the cause of such cancer, it would have been detected long before now.<P>
 
There are lots of different types of DNases and RNases in cells!
Click to expand...
I only said that because I was conceding a point made by zyncod. I wasn't sure, but still wasn't convinced, and didn't really have a point to argue with.
 
Actually, my point was simply that DNases are not embedded in cellular membranes - ever. Of course you can find DNases throughout the cell. And as to Hercules Rockefeller, no, DNA does not in 99.9% of cases enter intestinal epithelial cells. However, as someone (in upstate NY) who has found zebra DNA incorporated in bacterial DNA in the course of routine cloning experiments, I would have to say that nothing is impossible.
 
Well, by "within the cell membrane" I meant inside the cell. I assumed that was clear.

You are comparing bacteria to human cells. This is not valid. Bacteria, not even all bacteria mind you, I believe it's only gram negative, frequently transform and incorporate DNA from their environment. Eukaryotic cells do not. They destroy DNA down to the nucleotides and use those to build up their own DNA during replication and repair.
 
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Actually only a few bacteria are known to be naturally competent, as e.g. Bacillus subtilis, which is gram-positive, and some can be made competent, e.g. E. coli (gram negative). But as already pointed out, mere uptake is not sufficient to have any futher effects. Bacteria do this regularly (unless their restriction system strikes first), eukaryotic cells usually not.
 
If the insertion of ingested foreign DNA was the cause of such cancer, it would have been detected long before now.
Click to expand...
i was just stating tat as an example
and there might be a tiny winy chance tat it has not been detected yet.
oh ok...i think i am just looking out for an argument
i needed some topic to write an essay on..
so thought this was a good idea
will it do..?
 
It is not true that eukaryotic cells destroy all DNA that gets into the cells. For example, many of the genes encoded by primitive mitochondria, have, over the past billion years, transferred into the host genome (our own genome), a process that would be impossible if all cytoplasmic DNA was destroyed. And there is a bacterium (Agrobacterium tumefaciens - Monsanto really loves this guy) that induces a 'cancer,' of sorts, in plants by transferring some of its own DNA into the plant genome - but it does not actually enter or pierce the nuclear membrane. And all DNA viruses (eg, smallpox, polio, etc) that infect us must transfer their DNA outside the nucleus to either protein coats or 'budding' sites on the plasma membrane. So, no, not all DNA in the cytoplasm is destroyed and eukaryotes are capable of taking up DNA to integrate in the genome. Of course, as I've said before, the chances of this happening are almost vanishingly small since
1) DNA is a polar molecule and polar molecules can't really pass through the cellular membrane
2) Most DNA in the cytoplasm is destroyed by DNAses
3) Even in the nucleus, foreign DNA is very unlikely to be spliced into the genome.
But it has happened (see the mitochondria). And I was never comparing the process of transformation in bacteria to what we're talking about here - competent bacteria have specialized apparati to transfer plasmids which would be incredibly stupid to keep in multicellular organisms. And by the way, in biology at least, when you say "in the membrane," you mean "in the membrane," that is, embedded in the membrane. Cytoplasmic or intracellular would be more concise and far more accurate ways of saying what you meant, Idle Mind.
Oh, and swetha, the transfer of genes from mitochondria to the nucleus would, I think, be an excellent topic for a paper. It is extremely interesting, and puzzling, why another organism (the mitochondrion) would cede genetic control to us, the eukaryotes. I don't know if you are aware of this, but mitochondria - the organelles that make it possible for us to breathe oxygen and thus to be multicellular, were likely bacteria that were "eaten" by our eukaryotic ancestors about a billion years ago. Same with chloroplasts in plants.
 
thank u sooo much for that bit of infomation....i hadnt actually thought about the mitochondria..this is just grt!
 
mayb the mitochondria decided that it wud survive better if it let the eukaryotic cell take care of it.....similar to symbiosis....?
 
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