A letter from Bennett Greenspan, FamilyTreeDNA Founder

[customerserviceguy]

13. The bottom line is

you get half of your father's genes and half of your mother's genes. Which half you get is by pure random chance, and that's why siblings (except for identical twins) are not like clones.

And you are quite correct in saying that certainly not all of our genes pass to the next generation, but the more offspring a person has, the greater the chances that the complete genome get passed on to someone in the next generation. My work often involves French-Canadian farmers who had ten to twenty or so children, so the chance that nearly 100% of their genome got passed is pretty high.

Also, the more siblings sampled, the better, you are quite correct on that point.

Still, the combination of DNA testing plus traditional "paper" genealogy gives the best possible answers to who genetic forebears are. For most people, an accurate picture of their pedigree can indeed be produced, and verified by DNA testing.