The XX configuration is tricky, which many either forget or do not realize. The Y-gene is so easy to follow because it always comes directly from father to son, father to son, at so on. My Y-gene is the exact same one my several times great-grandfather had (unless some genetic mutation occurred in between).
With a female child, each parent contributes an X gene. Which grandmother that particular X gene came from is another matter. The X gene passed father to daughter had to come from the father's mother; however, she had an X gene from each parent, so the X gene the father passed on could have come either from his mother's mother or his mother's father. In turn, that X gene could have come from different grandmothers. What this means is full sisters can have different X genes via their mother, as the one from their mother passed could have come from any one of three grandmothers (either of two passed from the mother's parents or one passed by the father)! Add in great-grandmothers and it's even more complicated. In the case presented here, the fathers were different so the X gene each one passed could be from a different grandmother as well. Thus, we can see the importance of "triangulation" of getting DNA samples from first cousins for comparisons, in addition to that from siblings. Tomás Leal -- You received this message because you are subscribed to the Google Groups "Azores Genealogy" group. To unsubscribe from this group and stop receiving emails from it, send an email to azores+unsubscr...@googlegroups.com. Visit this group at https://groups.google.com/group/azores. To view this discussion on the web visit https://groups.google.com/d/msgid/azores/b90e1385-18d7-41b1-9ebb-799e6e5311fa%40googlegroups.com.
