Shared Chromosomes-Part 4 X-Chromosomes

In Shared Chromosomes Part 2 we saw how easy it was to discover on which side of the family a match was when parents are included in DNA testing and how it is even better when grand-parents are tested.
In Shared Chromosomes Part 3 we saw how testing 1st and even 2nd cousins also helped direct us to which side of the family a match originates.

In this segment, Shared Chromosomes Part 4 we will visit how using X-Chromosomes can reveal matches on the maternal side of one’s family. When showing a match is on one’s Maternal side the match eliminates the possibility the match is on the Paternal side.
The following table shows how many total matches each of the seven cousins have, how many X-Chromosomes each cousin has and how many of those X-Chromosomes are shared with one or more of the their cousins.
Cousin Total Matches Total X-Chromosomes Shared X-Chromosomes
Fran              1241                 279                                    54
Cliff               1392                 020                                    17
Mic                1298                 023                                    15
Rita                1459                287                                     29
Peggy             1162                271                                    30
Bud                1533                008                                      0
Chuck            1064                004                                      0

The following table shows the distribution of the shared X-Chromosomes.
Cousin Shared X-Chromosomes
Fran-Cliff                     3
Fran-Mic                      2
Fran-Rita                    21
Fran-Peggy                24
Fran-Bud                     0
Fran-Chuck                  0
Cliff-Mic                       7
Cliff-Rita                       1
Cliff-Peggy                   1
Cliff-Bud                       0
Cliff-Chuck                   0
Mic-Rita                        1
Mic-Peggy                    1
Mic-Bud                        0
Mic-Chuck                    0
Rita-Peggy                    2
Peggy-Bud                    0
Peggy-Chuck                0
Fran-Mic-Cliff               1
Cliff-Mic-Peggy             1
Cliff-Mic-Rita                1
Fran-Mic-Rita               1
Fran-Cliff-Rita              1

Notice Chuck and Bud share no X-Chromosome between themselves or with anyone else in the Cousin familial group. This is because males inherit a Y-chromosome from their father and an X-Chromosome from their mother. In the case of both Bud and Chuck the relationship between them and to the other cousins is through their respective fathers. Therefore, there is no X-Chromosome to share.
Mic and Cliff are males and inherited a Y-Chromosome from their father and an X-Chromosome from their mother. Fran, the sister, inherited two X-Chromosomes, one from her mother and one from her father. Her X-Chromosome matches can come from either her paternal or maternal side of the family. Any match between Fran, Mic and Cliff will only come from their maternal side of the family.
Peggy inherited one of her X-Chromosomes from her mother and one from her father. Her mother was a sister of Mic, Cliff and Fran’s father. Fran inherited this same X-Chromosome from her father. Mic and Cliff did not.
Any X-Chromosome match between Fran and Peggy will be from Peggy’s Mother and Fran’s Father who were siblings and the X-chromosome between them will come from their mother’s side which was the common Grandmother of Fran and Peggy.

The X-Chromosome Peggy inherited from her father has no relationship to any other cousin in the Cousin Familial Group and is not involved in this study.
On the maternal side of Fran, Mic and Cliff’s family, their cousin, Rita, inherited her mother’s X-Chromosome. This is the same X-Chromosome each of the siblings Fran, Mic and Cliff inherited from their mother. Thus, Fran, Mic, Cliff and Rita all share the X-Chromosome of their common Grandmother. Any match between them will be through that Grandmother, their maternal side both their families.
In the table above there are some X-chromosome matches shown between Mic and Peggy and Cliff and Peggy. As these matches can not occur, they need to be investigated and reported on in future blog.
A while back I posted a blog about “Finding X-Chromosomes” on this website. As a shortcut you may click on the link http://micsxchromosome.micbarnette.com/x-chromosomes/ to take you to that blog.

Concentrate on where on a pedigree chart one may inherit x-chromosomes. Also pay attention to the Ahnentafel numbers. X-Chromosomes can only be inherited from certain ancestors having certain Ahnentafel numbers on a pedigree chart.
As stated earlier in this article, I hope I have made your research easier and you are able to move on out further on more limbs of your tree.