I was just thinking if the 15 matches that Madeleine had do they all have to match some parts of her parent's DNA.
Is it, if she is a daughter all those matches will be covered in Gerry's or Kate's DNA.
I am so green on the subject I don't even know what they were matching.
As I said before this is a learning exercise for me.
There were 20 places where madeleine's DNA should have matched either Gerry's or Kate's but since they shared one site themselves there was a total of 19 sites to match. I understand that bit. But there ended up being many more portions than required which showed the sample was made up from more than 1 person.
Did you understand what they said about that?
Are you confusing the surrogate reference / later reference samples with the sample found in the boot?
The reference samples were analysed to determine what her DNA profile was, using the UK's standard nuclear forensic DNA test.
The boot sample was different: it was to analyse the DNA results of whatever was found in the boot. In the boot, they found a total of 37 alleles at the 10 marker / loci (locations) used by the UK's forensic service. Out of a hypothetical total of 20 alleles - in her case 19 due to the fact that she inherited an identical allele value from both parents - they found that there were 37 allele values in total and that therefore several people had left their DNA in that sample.
Individual alleles are not unique to a single individual: you and I may easily share 6 or more individual ones (even in the small number of locations searched for forensic purposes). We may even share two alleles at the same marker / loci (location), and I doubt very much that we are related. If we were related, we may well share more than that. It's the combination of the totality of the alleles found at the specific locations that distinguish one person from another for most intents and purposes.
There have been mistakes in the past when forensic DNA was first used as, at least in the UK, they only looked at 6 markers instead of the current 10. Forensic services in several other countries look at more than 10, but they are not always identical locations. The last time I looked, Interpol still had a database of 6, but there may be several reasons for that.
I'm not sure if my attempts at explaining will be of any help:http://miscarriageofjustice.co/index.php?topic=6311.msg273406#msg273406
There's more on pp. 403-405 as well.