DNA profiling.

Having disposed of the Monty Hall problem (or at least I hope so) let's move on to another area where probability is a factor - DNA profiling. Now I am not arguing for or against, but what concerns me is that this is an area where there is considerable confusion in the public mind (and I have to say that much of it appears to be deliberately engendered) and this confusion is in great part probability based. So, to start at the very beginning ("a very good place to start") over 99.9% of your DNA and mine is identical - it's what makes us human beings, rather than dogs, or fish, or worms or whatever. So only a minute fraction - around 0.1% - distinguishes you from me. Despite the smallness of this percentage, it still represents an enormous amount of DNA material - far too much for it to be realistic to carry out a complete comparison. So what scientists do is to look at little bits of this material, where experience has taught them that differences are most likely to occur, and this produces what has become known as our DNA profile. Now whilst - excluding identical twins - as far as anybody knows, your DNA is unique to you, it by no means follows that your DNA profile is. More next time...