Probably a stupid question...

If humans are omnivores and eat a wide range of plants and animals, then why when people give DNA tests aren't the human DNA strands mixed in with loads of plant and animal DNA?

If I eat a chicken breast, surely that contained chicken DNA. When I eat it, and the proteins, etc. work their way around my body, what happens to the chicken DNA? Same with vegetables, fruits, etc. In fact, pretty much everything we eat!

The food we eat get broken down into carbohydrates, fatty acids, amino acids, etc. in the digestive system and get absorbed into the circulatory system. The blood then carries these to the cells in our body where they are further transformed into things the cells can use, like glucose and then enerygy. Protein gets broken down into amino acids which is then used to creat our own proteins in our cells.

So our body is built on the compounds that make up food, i.e. amino acids, etc.

As for DNA, DNA is very fragile, so it would be one of the first things to be broken down during digestion. So even if we use DNA from external sources (I'm not really sure if that's the case) it'd be likely that we use the individual DNA, rather than strands of DNA.

All life, with a few minor exceptions, uses the same four basic components to build DNA - the nucleotides adenine (A) guanine (G) cytosine (C) and thymine (T).

When we eat food, it is rich in non-human DNA. In our digestive system, this DNA gets broken down into its components - the nucleotides ATC and G - these can get broken down even further into smaller molecules, which are reassembled by our cells to make all sorts of things, including new nucleotides. Sometimes nucleotides get recycled. Whatever their provenance, recycled or synthesized de novo, these nucleotides get restrung together in our cells to form strands of DNA identical to the DNA already in our cells. That is, they get made into human DNA, whatever their source.

Last edited by Ajna Rivera (28th Apr 2010 14:30:38)

"All life, with a few minor exceptions, uses the same four basic components to build DNA."

There are exceptions to this?! Do tell!

Mike,

I guess it depends how strictly we want to define the nucleotides, because there is also 5-methylcytosine and 5-hydroxymethylcytosine, both of which have unique properties, and thus distinguish them from regualr old cytosine; in the same way that thymine is essentially methylated uracil.

There was some coverage of 5-hydroymethylcyctosine last year.

...I think it could be some time before we see any 'artificial' life generated using the new artificial DNA bases that have been in the literature for the past few years.

Thanks Jim, that's what I was thinking of -
there are a couple other weirdo examples as well.  One other that is
really interesting is the potential use of Uracil in DNA as a signal.

But whatever the nucleotide, it mostly gets smashed during digestion and used to make new molecules specific to the host organism.

Last edited by Ajna Rivera (12th May 2010 16:20:13)

We can also have immune (e.g., T-cell and antibody) responses to some
types of ingested, foreign DNA which has implications for oral DNA
vaccines. Also, see below re. discussion on fate of ingested DNA -

http://www.psrast.org/jcfateofgen.htm