[dono (OP)]

HOW IS DNA FROM DIFFERENT INDIVIDUALS SEPARATED FROM A SINGLE SAMPLE FOR DNA FINGERPRINTING?

In a biological sample such as blood, I assume there might be DNA from various bacteria and viruses, in addition to the donor's DNA.

In a crime scene, I don't want to imagine the situation, I assume it is possible that the sample might contain DNA from several individuals.

Don't you have to start with the DNA from a single individual (human or otherwise) before you do DNA fingerprinting?  How is the DNA from different individuals separated?

Just as people are DNA fingerprinted, is the same done for disease organisms?  If I get the flu, hos do you find out which flu virus I have?  Again, how do you separate the DNA from different viruses or bacteria?

Do scientists have a database of DNA fingerprints for viruses?

Thanks, dono

[rosy]

There are people out there better qualified than me to answer this but I believe the reason is that they only look at certain sections of the genetic material and do a sort of "photocopying" reaction (I've forgotten the proper term) which makes many copies of the bits they're interested so that they swamp out not just DNA from other people/organisms but also the rest of the DNA from that individual.
Then they cut up the bits they're looking at with an enzyme and look at the patterns they make in some kind of gel chromatography.

Um, it's a bit late, and I'm a bit tired, for a proper explanation but if you want to know more just ask.

[chris]

This article, by Chris Smith and Dalya Rosner, gives a step by step guide to genetic (DNA) fingerprinting:

http://www.thenakedscientists.com/HTML/articles/article/dalyacolumn8.htm

[Mjhavok]

Thanks Chris