How many markers do you need? How accurate is it?

The more markers the merrier, although many people like to start with a low-resolution test and then pay for an upgrade if and when they got a low-resolution match, to explore it further. Since the individual mutations are random events, you might be 'unlucky' and have several mutations within your family tree. Studies so far indicate that close family relatives should be identical or near identical up to 37 or 43 markers. On the other hand it has happened that two brothers may differ although this would be very rare. At lower resolution (i.e. 10 or 12 markers), matches may turn out to be spurious as there is insufficient differentiation. This is particularly so if you come from the dominant haplotype group known as 'R1b' which is common in Western European ancestry. The tests are not yet accurate enough to prove 100% the exact generation in the family treee.