Mtdna Test
MtDNA tests are almost the opposite of Y-STR tests, in that they are primarily and in the majority used to determine genetic maternal relationships or 'lineage', rather than paternal. Unlike Y-STR testing, mtDNA can be passed from the Mother to both Daughters and Sons, so both men and women can trace their maternal lineage if they have obtained a DNA sample from either their mother or maternal grandmother.
This kind of test can only be carried out with samples from both the child and the suspected mother or maternal grandmother. Once these are obtained and sent to a laboratory a trained forensic scientist will 'sequence' both samples, I.e. he or she will determine what pattern or order the DNA molecules fall into, and then compare the two results. Once these two results have been found they are then compared to the 'Cambridge Reference Sequence' or 'CRS', which is essentially a universal European typical DNA sequence. The differences found between the CRS and the samples are highlighted and then any of the same differences between the two samples taken from suspected mother and child are observed to find any of the same confounding DNA patterns. This may sound like a meticulous, fiddly and unreliable method but in fact the results are so specific and the way that mother and child share DNA is so predictable that the results are almost 100% correct.
The majority of mtDNA test samples use the HVR1 and/or HVR2 hyper variable regions (locations within DNA whose molecules can be strongly indicative of lineage or mutations). This basically means that laboratory mtDNA tests use the most reliable and clear part of the DNA to extract results. This remarkably popular method of DNA testing is made stronger by the fact that a father cannot pass on mtDNA sequences, so any maternal relationship found is 50% more reliable.