To Andrews point, the technology can't help you go further back since mathematically you can only halve a finite number of genes so many times. To Paulo's point, no,.it is not a flaw of adna that you can only go back so far anymore that a hammer is flawed because it can't brush your teeth Joe c

On Saturday, August 26, 2017 at 11:11:59 AM UTC-7, joe...@gmail.com wrote: > To Andrews point, the technology can't help you go further back since mathematically you can only halve a finite number of genes so many times. > > To Paulo's point, no,.it is not a flaw of adna that you can only go back so far anymore that a hammer is flawed because it can't brush your teeth > > Joe c In actuality the statistics on this point is not correct. Or rather it's both correct and not correct. The genes do not half. You don't inherit a half-gene. The segments, on average, and viewed globally, can be inherited in half pieces, however there is a limit to that. There is not going to be a case where you inherit, in a string of ten base pairs, one base pair from randomly disconnected ancestors. That's the problem with this viewpoint. What is actually seen, is segments being based down, sometimes for three generations, completely intact, while others are broken up. These sticky segments, which are different for each person, can point at a ancestral pair three hundred years in the past. Perhaps even six hundred years. The actual situation is murky at present. That we don't know who they are just yet, is not the same as saying they don't exist.

On Saturday, August 26, 2017 at 11:47:34 AM UTC-7, wjhonson wrote: > In actuality the statistics on this point is not correct. > Or rather it's both correct and not correct. > > The genes do not half. You don't inherit a half-gene. Actually, they sometimes do, and you sometimes do. There are two types of crossovers that drive the 'halving', and one of them takes no notice whatsoever of where gene boundaries are - it is completely random. The other is not random, having hotspots and deserts, but it isn't entirely clear what defines these - it is not boundaries between individual genes, which for the most part don't exist, with the possibility of the same DNA being part of two different genes, but may be the boundaries of 'regulatory blocks' that include several full genes - that is just a guess, but it may be a valid one. > The segments, on average, and viewed globally, can be inherited in half > pieces, however there is a limit to that. There is not going to be a case > where you inherit, in a string of ten base pairs, one base pair from > randomly disconnected ancestors. In fact, the smallest divisible segments are probably in the 10s to 100s of thousands of bases, which is what puts a definite limit on the number of generations over which autosomal is likely to be informative without a huge amount of luck (for every ancestor from 1600 from whom you have a detectable preserved block, you have many more ancestors from whom you inherit no DNA whatsoever). These blocks pass intact for an incredibly long time, the block that includes the gene determining the most common form of blue eyes is about 150,000bp long and to have passed largely intact for more than 12,000 years. This presents a problem on two sides - relatively close relative may not share the block at all. If two people do share the block, it shows they are related, but perhaps too distantly to be genealogically relevant. taf