RootsWeb.com Mailing Lists
Total: 3/3
    1. [AUTOSOMAL-DNA] Question about X-DNA and sisters
    2. Greg Lovelace
    3. Greetings, all. I am working on a project that I need a little help on. I've tried going through all the DNA blogs and still can't come up with a definitive answer, so I'm hoping some of you have faced this situation and can give some guidance. I am looking at two sisters and their female 1st cousin. The sisters (call them "A" [Shirley] and "B" [Boni]) were raised as full siblings. However, they only share ~1700 cM of DNA at the 5cM threshold, indicating to me that they are only half-siblings. Is this a correct assumption? Now the cousin (call her "C" [Doreen]) and "A" share ~860 cM of DNA, placing them correctly as full first cousins (the average for 1st cousins is 874 cM). The father of "A" and "B" is the brother of the mother of "C." At the 5 cM threshold, "B" and "C" have no shared segments of DNA. And "A" and "B" only share about 50% of the DNA on their X-chromosome, indicating to me that they only share one parent. Is that a valid assumption? Thanks for any insights. Peace, Greg Lovelace Part of the Tree Research Services 683 Edmonds Drive Charleston, SC 29412 <mailto:[email protected]> [email protected] <http://www.part-of-the-tree.com/> www.part-of-the-tree.com

    01/23/2018 07:41:18
    1. Re: [AUTOSOMAL-DNA] Question about X-DNA and sisters
    2. Tim Janzen
    3. Dear Greg, If you look at Blaine Bettinger's chart at https://thegeneticgenealogist.com/wp-content/uploads/2017/08/Relationship_Ch art_FINAL_August_2017.jpg you will see that he doesn't have any data indicating that full siblings share anything less than 2209 cMs. There could be situations where full siblings share less than that, but I agree with your conclusion that A and B are 1/2 siblings. The fact that B and C share no autosomal DNA at a 5 cM threshold means that that can't be any more closely related than 2nd cousin once removed. It would appear that A and B share the same mother, but that A and B don't share the same father. The father of A is the brother of the mother of C, but the father of B isn't closely related to either A or C. Inheritance of the X chromosome among siblings can be variable. If two sisters have fully-identical regions then they are very likely to be full sisters, but apparently A and B don't share any fully-identical regions. Sincerely, Tim Janzen -----Original Message----- From: AUTOSOMAL-DNA [mailto:[email protected]] On Behalf Of Greg Lovelace Sent: Tuesday, January 23, 2018 11:41 AM To: [email protected] Subject: [AUTOSOMAL-DNA] Question about X-DNA and sisters Greetings, all. I am working on a project that I need a little help on. I've tried going through all the DNA blogs and still can't come up with a definitive answer, so I'm hoping some of you have faced this situation and can give some guidance. I am looking at two sisters and their female 1st cousin. The sisters (call them "A" [Shirley] and "B" [Boni]) were raised as full siblings. However, they only share ~1700 cM of DNA at the 5cM threshold, indicating to me that they are only half-siblings. Is this a correct assumption? Now the cousin (call her "C" [Doreen]) and "A" share ~860 cM of DNA, placing them correctly as full first cousins (the average for 1st cousins is 874 cM). The father of "A" and "B" is the brother of the mother of "C." At the 5 cM threshold, "B" and "C" have no shared segments of DNA. And "A" and "B" only share about 50% of the DNA on their X-chromosome, indicating to me that they only share one parent. Is that a valid assumption? Thanks for any insights. Peace, Greg Lovelace Part of the Tree Research Services 683 Edmonds Drive Charleston, SC 29412 <mailto:[email protected]> [email protected] <http://www.part-of-the-tree.com/> www.part-of-the-tree.com ______________________________ For answers to Frequently Asked Questions about mailing lists, please see: http://dgmweb.net/MailingListFAQs.html ------------------------------- To unsubscribe from the list, please send an email to [email protected] with the word 'unsubscribe' without the quotes in the subject and the body of the message

    01/23/2018 05:41:37
    1. Re: [AUTOSOMAL-DNA] Question about X-DNA and sisters
    2. Curtis Rogers
    3. Kitty Cooper has an outstanding analysis for determining half vs. full siblings: http://blog.kittycooper.com/2016/04/full-versus-half-sibling-dna-matches/#comment-444215 Curtis Rogers On Tue, Jan 23, 2018 at 2:41 PM, Greg Lovelace <[email protected]> wrote: > Greetings, all. > > I am working on a project that I need a little help on. I've tried going > through all the DNA blogs and still can't come up with a definitive answer, > so I'm hoping some of you have faced this situation and can give some > guidance. > > > > I am looking at two sisters and their female 1st cousin. The sisters (call > them "A" [Shirley] and "B" [Boni]) were raised as full siblings. However, > they only share ~1700 cM of DNA at the 5cM threshold, indicating to me that > they are only half-siblings. Is this a correct assumption? > > > > Now the cousin (call her "C" [Doreen]) and "A" share ~860 cM of DNA, > placing > them correctly as full first cousins (the average for 1st cousins is 874 > cM). The father of "A" and "B" is the brother of the mother of "C." At > the > 5 cM threshold, "B" and "C" have no shared segments of DNA. And "A" and > "B" > only share about 50% of the DNA on their X-chromosome, indicating to me > that > they only share one parent. Is that a valid assumption? > > > > Thanks for any insights. > > > > Peace, > > Greg Lovelace > > Part of the Tree Research Services > > 683 Edmonds Drive > > Charleston, SC 29412 > > <mailto:[email protected]> [email protected] > > <http://www.part-of-the-tree.com/> www.part-of-the-tree.com > > > > > > ______________________________ > For answers to Frequently Asked Questions about mailing lists, please see: > http://dgmweb.net/MailingListFAQs.html > > > ------------------------------- > To unsubscribe from the list, please send an email to > [email protected] with the word 'unsubscribe' without > the quotes in the subject and the body of the message > --

    01/24/2018 01:35:32