Genetic Genealogy: Chapter 6

 Genealogical Applications for X-DNA

Chart from Appendix A; marked for X. Use for Q 1-7

1. Which ancestors shown may have contributed to the X-DNA of Ira Gerball (20)?

15, Marie Small. Men get no X-DNA from their fathers, only their mothers. Marie's ancestors are not in the chart. 4

2. Which ancestors shown may have contributed to the X-DNA of Mandella Louise Smith (33)? Would Mandella have inherited X-DNA from all of these possible ancestors?

Since Mandella is female, she got X-DNA from both her parents, 21 & 27. The X she got from her father 27 came from his mother who is not shown in the chart. The X from her mother Mandy Wick 21 is from her parents, 12 & 16. Again, her father Tom Wick 16 got his X from his mother who is not shown in the chart. Mandy's mother Emma Crocker 12 got her X-DNA from both her parents, 5 & 8. And once again, her father Henry Crocker 8 got his X from his mother, but she is not in the chart. Her mother Emma Jones 5 got her X-DNA from both her father John Ira Jones 1 and her mother Mary Ann Smith 2. 

It is possible that Mandella got X-DNA from each of the listed ancestors, but since it can recombine every time a woman passes some X along to a child, it is up to chance. Siblings may inherit from entirely different possible ancestors.

3. Does Louis Gerball (32) share an X-DNA inheritance line with Mandella Louise Smith (33) through the ancestors shown on this chart?

No. Louis 32 gets his X-DNA from his mother, Ann Ricks 26 whose parents are not in the chart. Mandella 33 shares no X-DNA according to the chart.

4. Does Ira Ryan (43) share an X-DNA inheritance line with Mandella Louise Smith (33) through the ancestors shown on this chart?

Yes, they both share 1 & 2 Jones and Smith. His line goes though different people (31, 19, 11, 4) and there could have been some recombination, so it will not be identical.

5. Does Viola Scott (17) share an X-DNA inheritance line with Ellis Jones (10) through the ancestors shown on this chart?

Yes, Ellis Jones 10 gets his X-DNA from his mother Martha Jackson 6 whose parents are not in the chart. Viola Scott gets hers from 9, 13, 3, 6, 1 and 2, so they share Martha Jackson 6, their mother. His X will be 100% from his mother; Viola will have one from her father and the other, possibly recombined, from her mother.

6. Given the following X-DNA match results for Mandella Louise Smith (33), is the shared segment size large enough to focus research for a common ancestor on those who could have contributed to the X-DNA of those test-takers?

Yes, over 10 cM is worth investigating, and the other two smaller segments overlap. So *if* there is a shared X-DNA ancestral path, even the smaller ones are worth looking at.

7. Which ancestors shown on the chart are potential common ancestors who could have contributed the matching X-chromosome segment? 

Mandella Louise Smith (33) shares Emma Crocker (12) with Emmy Wick (34). Emma Crocker carries the X-DNA from both 1 & 2 Jones and Smith through her mother, Emma Jones (5). They also share Tom Wick (16) but would not have gotten a shared X-DNA segment from him, since he passed that segment from his mother only to Mandy Wick (21) whom is ancestral only to Mandella.

Mandella Louise Smith (33) shares an ancestral couple 1 & 2 Jones and Smith with both Violet Sweets (29) and Janice Johns (31). However, they will share only Smith 2 and not Jones 1 because his unrecombined X-DNA from his mother was not passed though Albert Jones (3) to Violet. Mandella will share both 1 & 2 Jones and Smith with Janice.

8. An X-DNA segment of a significant size is shared with Debbie, Debbie's full brother, and test-taker Allen Jackson. On which portions of the trees of these test-takers should the search for a common ancestor focus?

This question is identical to 9, below.

9. An X-DNA segment of a significant size is shared with Debbie, Debbie's half-brother (son of Debbie's mother), and test-taker Allen Jackson. On which portions of the trees of these test-takers should the search for a common ancestor focus?

The focus will be on the mothers - Debbie and her half-brother's shared mother, and Allen's mother, since neither man got an X from their father. It can further be focused by completing an X-DNA inheritance chart for both men.

10. An X-DNA segment of a significant size is shared with Debbie, Debbie's half-brother (son of Debbie's father), and test-taker Allen Jackson. On which portions of the trees of these test-takers should the search for a common ancestor focus?

For Debbie, all parts of her tree will have to be examined, because she got an X chromosome from both her mother and her father. The men did not get an X from their fathers, therefore only their mother's trees need to be examined. The search can further be focused by completing an X-DNA inheritance chart for Debbie and both men.