Crazy DNA question...

Doug · Oct 8, 2004

DNA identifies an individual, blood certainly works.

Lets say you donate blood, some guy receives it, He kills somebody, and in the process leaves some of his ( your ? ) blood behind. Could the police try to nail you for it ?

I think not, but I don't know enough about medicine to say why. Maybe they only use the plasma, and that doesn't have the DNA ? I know blood is replaced by bone marrow. Women obviously lose blood monthly.

Just a weird thought I had. I'll bet the average Joe doesn't know the answer.

drunkguy · Oct 8, 2004

red blood cells contain no nucleus and thus no DNA

other cells are present in the blood but less than 1% of total blood volume.
Not sure if the white blood cells (containing DNA) are also transferred during a transfusion.

An average person had about 5 liters of blood. Unless they are being transfused a huge amount of blood, the majority will still be their own. Also, they will continuous be making their own cells which would gradually replace the donor's.

Worst case scenario...the DNA sample would show 2 distinct fingerprints...one of the person donating blood, the other of the person's own DNA. That is IF the small amount of donor DNA is enough to even show up during the "DNA fingerprinting".

Interesting question though

are you planning on comitting a murder anytime soon?

BoratSagdiyev · Oct 8, 2004

Also same question goes for semen. If you make donation of semen who are you to say it won't be used by someone who put on womans vagine and then say "Hey it was him, make him have liquid explosion and then check him" This my friends is the dangerous part of DNA tests!

Doug · Oct 8, 2004

Borat Sagdiyev said:
Also same question goes for semen. If you make donation of semen who are you to say it won't be used by someone who put on womans vagine and then say "Hey it was him, make him have liquid explosion and then check him" This my friends is the dangerous part of DNA tests!

Borat: I didn't consider that possibility ! Moral of story becomes... if you sell your " stuff"... get a good price for it ! You may need to hire a lawyer later !

I'm sure the Red cross loves my post.

DarrylParsons · Oct 13, 2004

I recently read about this in a scientific forum, but unfortunately I don't remember where exactly.

An expert gave an answer to this and it's pretty much what drunkguy said...ie. only red blood cells are given in a transfusion, so no foreign DNA is introduced.

He also said something to the effect of: whenever there is foreign DNA in the body, the immune system kicks in and tries to kill the foreign cells.

Then someone asked...what about a bone marrow transplant? Isn't that foreign DNA? To this the expert answered (I'm paraphrasing again): Yes, but in that case the white blood cells are the donor's as well and so the immune system (which keys off the marrow apparently) does not regard them as foreign. The tissue of the recipient, however, is foreign, and to avoid immune system overreaction they normally give some drug to weaken the immune system somewhat.
I'm going on memory here so I hope I haven't botched this too badly. If someone in the know could correct me I'd appreciate it. That's the gist of it anyway. Very interesting question. Gotta love these forums -- way better than watching TV!!!