Bloody Transfusions and DNA

[MustangLady]

Ok, we all know that DNA is unique to each individual. Say for instance someone needed a blood transfusion, would they then have the DNA of the person the blood came from? Or if there is a mixed blood transfusion given, does the DNA change in the person to whom its been given? This has baffled me, I've been thinking about giving blood but don't want anyone to have my DNA.

[theprof]

These questions can't be answered by a simple yes or no because of the way they've been asked, but it's not your fault! I'll try to explain.

To start with, DNA can be regarded as occurring mainly in the nuclei of cells (I'll leave out mtDNA here)

Going back to basics, blood is composed principally of white blood cells, red blood cells, platelets and plasma.

Now virtually all blood transfusions are transfusions of mainly red blood cells along with plasma (the liquid part of the blood). I say mainly because it's not impossible for this type of blood transfusion to contain the odd white blood cell.

Circulating red blood cells do not contain cell nuclei, chromosomes or DNA. Therefore, in normal blood transfusion you are very unlikely to donate your DNA to the recipient of your blood.

A whole blood transfusion contains white blood cells, red blood cells, platelets and plasma.

Now white blood cells do contain cell nuclei, chromosomes and DNA, so you will donate your DNA to the recipient.

However, there's really no need to be concerned for a number of reasons.

Firstly, it's simply not possible for donor DNA from white blood cells to combine with the DNA of the recipient's white blood cells and divide into daughter cells containing both types of DNA.

Secondly, white blood cells have a very unpredictable lifespan in the body which is governed by the function of the different types. Some last only hours, whilst others last years. However, because they cannot combine with the white blood cells of the recipient, they are effectively doomed as soon as they enter the bloodstream with their DNA locked away inside them.

Thirdly, whole blood transfusions are only very rarely needed in patients.

So in effect, normal blood transfusions will not give the recipient your DNA and in full blood transfusions, your

[theprof]

DNA will neither change nor combine with the DNA of the recipient.

Either way, both red and white blood cells have a limited lifespan and even in a whole blood transfusion, no trace of the majority of your blood cells and the DNA they contained would be found in the recipient after a few months.

Isolation of foreign DNA in the bloodstream of the recipient following blood transfusion is highly experimental and is fraught with analysis difficulties.

[kempie]

BTW who is able to give an absolute guarantee that the DNA sequences found within the human genome are unique to each individual?

The probability of two (or more) persons possessing identical DNA profiles may well be extremely small but that does not rule out the possibility, especially when you consider that only a handful of DNA regions are mapped to produce the DNA profile claimed by many to be the Holy Grail of prosecutorial evidence.

http://www.ornl.gov/sci/techresources/Human_Ge nome/elsi/forensics.shtml

[StudentGal]

It is unfortunately shows like CSI, NCIS etc that have propelled this thought of DNA profiles being the be all and end all of criminal prosecutions into the public limelight. I can assure you that after completeing 2 years of university studying in a forensic field that it has been drilled into me that DNA profiles are not conclusive evidence. In the UK, the DNA profiles created have a calulated match probablility of 1 in 1 billion (American billion so one thousand million). This is the probablility of the profile matched to the scene sample being shared at random by two unrelated individuals. So I can vouch that in the professional field, DNA evidence is considered in the correct context as supportive evidence.

The ENTIRE sequence of DNA in a human body is uniqe (apart from identical twins who have identical DNA too) as that is why we are all marginally different to one another but agreed the sequences used for DNA profiling are not completely unique and that's wht the match probablility has to be calulated.

[MustangLady]

Good heavens - how complex these answers are... much more than i ever imagined to get back. Thank you so much to each of you for putting my mind at rest. I will confidently and happily be a blood donor now. I was worried that some 'criminal' could be given my blood (although a slim chance of this, but possibly never the same) and commit a crime for which I could be connected. You never know what could happen. But thank you again.