We seem to need periodic refreshers on just what DNA research involves, and what it can and cannot prove.
There are basically three type of DNA being researched:
Y-DNA:
Found on male Y chromosome
Passed on male to male to male ONLY.
Can show whether or not a tested male subject belongs to a family with other tested members.
CanNOT prove a direct relationship (it isn't *that* precise, yet), so you still need a good paper trail.
Absolutely no use in documenting mixed male/female descent.
mtDNA:
Found in female mitochondria, passed on via X chromosome.
Passed on female to female to female - sons can inherit but cannot pass it on.
Can show whether or not a tested female subject belongs to a family with other tested members.
CanNOT prove a direct relationship (it isn't *that* precise, yet), so you still need a good paper trail.
Not useful in documenting mixed male/female descent *except* when there is only one male link at each end and none in between.
Autosomal DNA:
Represents *all* genes/chromosomes.
Passed on randomly to male and female descendants alike.
Can be used to study mixed male/female descent, *but*....
Is randomly recombined with each new generation.
Can indicate that two tested people may be related, but not how (need as complete a paper trail as you can get).
Is increasingly insensitive and uninformative past about 5-7 generations.
*Does not have haplogroups*. Only Y and mtDNA have haplogroups - and they are different.
