How many genes for a genetic fingerprint?

18 March 2014

Question

How many genes do you need to give each person a unique genetic fingerprint?

Answer

Chris - The answer is, it actually takes none because the way in which they made and this is Alec Jeffreys who got a medal actually for the discovery of the concept of genetic fingerprinting back in the later 1980s. The way this works is that you use a part of your genetic code called VNTR's - Variable Number Tandem Repeats. There are some parts of your genetic code that don't code directly for a protein which you could detect in your cells. That's what genes normally do. So, you've got other bits of your DNA that don't code for things like that. Because they don't code for things, if changes happen to them, it doesn't matter to how the cell works. And so, certain bits of genetic sequence in those particular regions can be copied many, many times and it doesn't matter because it doesn't affect how the cell works. So, one person might have 15 copies and another person might have 500. If you cut the DNA up with molecular pairs of scissors called restriction enzymes, and they cut in various places in amongst these so-called variable number tandem repeats, you will get chunks of DNA of different sizes for every single person. And that's how a genetic fingerprint works. We're not necessarily sequencing genes although we can these days. Actually, those genetic fingerprints were based on random amplifications or copies of bits of DNA that don't actually necessarily do anything.

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