My son has a question

[Big Al1st]

If a man commits a crime and leaves some blood at the scene he can be caught by DNA. If he has had a blood transfusion a few days prior whose DNA is in the blood his or the donors?

[spk]

Hi Big Al- Ive just finished reading Bill Bryson A short history of everything and he talks about DNA in it alot which might help your son but what I think from what I gathered is that the DNA in the blood would be the mans because his body would adapt and change the DNA to match and coincide with all the other DNA in his body. Not sure if Im right but youve made me think !!

[PinkFizz]

Oooh,what a good question!

[spk]

Isnt it?! Im going back over that chapter now looking for the answer aargggh ! Thats going to keep me awake ! x

[Robinia]

When I had blood transfusions I think I was told that it takes the body about three weeks for the blood to become completely 'your own' but I've no idea what shows up during tests....fascinating, I'll look into it.

[JustSia]

No, as it would require a total blood transfusion which are really rare. And even then it is unlikely.

Normal blood transfusions are done using erythrocytes, which do not carry DNA and whose only function is gas exchange (i.e. oxygen and carbon dioxide). The bits that carry DNA are called leukocytes and those are separated away.

I found this article which I think will explain it in more detail. http://www.straightdope.com/mailbag/mblood.html

It also mentions the bone marrow transplant, which I think would be of interest to your son.

S.

[spk]

Genius Justsia thanks !!

[Big Al1st]

Thanks evryone particularly Justia. A very interesting and easy to read article. I will pass the link onto my son. Take care evryone Al

[mycats]

Thats one of the most interesting questions we have had on here for AGES :-)

[jon1968]

Just going to say the same thing as Mycats - what a fantastic question!!
Trust a kiddy to come up with an intelligent Q!!