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the "X" girls get from Dad

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  • the "X" girls get from Dad

    OK, I understand that males inherit their "Y" directly, and unchanged (inperfect world) from Dad.

    My question is, do females inherit the same "X"

    i.e. - do sisters have identical (in perfect world "X") on chromosome 23 ????

  • #2
    Short answer, No.

    Males have an X and a Y. They get the Y from their father and the X from their mother. As fathers they pass their Y to their sons and their X to their daughters. Because males have only one X, it cannot recombine, and so is preserved just as they got it from their mother.

    Females have two X's, getting one from their father and one from their mother. As per above, the X from their father is an unaltered transmission from their father's mother, grandma. On the other hand, their mother, a female, has two X's that can recombine so that every X a mother bequeaths is a unique product of recombination, or different from any other X she bequeaths to either a son or a daughter.
    Last edited by tomcat; 23 September 2009, 03:10 PM.

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    • #3
      Hmm. I didn't know about this before. I think the answer is yes. If a man has only one X to pass on to his daughters then all his daughters would have at least one of their Xs be identical because it came from their father. Their other X comes from their mother, but since their mother has two Xs (i will call them momX1 and momX2), the daughters will each have only one of moms two. Three daughters of the same parents will all have identical dadx. Each daughter would also have momX1 OR momX2. Am I right? I have ordered the 23andme test and it has an x test. If my ancestry painting shows that I have Native American autosomal ancestry but none on the x chromosone, that would mean that my Native American ancestry is from my fathers father? Or still a 50/50 chance the autosomes are from my paternal grandmother even if the x my father passed to me from his mother wasn't the NA one of the two his mother has? If his mom had one European X and one Native American X, but passed the European x to her son.
      Last edited by rainbow; 24 September 2009, 11:15 AM.

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      • #4
        For females one X is silenced in the autosome so that it does not interfere with the operations of the X not silenced. So, functionally, females have a single X. However in ovogenesis both X are active and do recombine. Hence every X a female bequeaths to any offspring is one-of-a-kind.

        Gene tests sample the autosome and so sample both X in females. Sisters would have an X in common that is the X that came from their common father and is unchanged from the X their common paternal grandmother bequeathed to their common father. The other X, from their common mother, would vary as it is a one-of-a-kind product of recombination.

        If those sister become mothers, the X's they pass-on are recombined products of the X's they received from their two parents.

        So the short answer is Yes and No. The X from a common father is common but the X contribution from the common mother is not.
        Last edited by tomcat; 24 September 2009, 11:31 AM.

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        • #5
          Is it known whether or not phenotype/looks are influenced by x? My mom most closely resembles her fathers mother. Would that indicate that the x she got from her father is her dominant x?

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          • #6
            I think the 1/4 of her entire genome received from her paternal grandmother would better explain any resemblance.

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            • #7
              Okay. Thanks for answering my question. I still wonder about what info the x holds. I guess I will find out about mine when my 23andme test is done. About my moms phenotype, instead of 1/4, most likely 3/4. My mom is a brunette. Three of her grandparents were brunet/brunette. Her maternal grandmother was the blonde. But my mom looks so much like her paternal grandmother that I think she got some extra or stronger genes from her.
              Last edited by rainbow; 24 September 2009, 04:09 PM.

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              • #8
                Originally posted by rainbow View Post
                Okay. Thanks for answering my question. I still wonder about what info the x holds. I guess I will find out about mine when my 23andme test is done. About my moms phenotype, instead of 1/4, most likely 3/4. My mom is a brunette. Three of her grandparents were brunet/brunette. Her maternal grandmother was the blonde. But my mom looks so much like her paternal grandmother that I think she got some extra or stronger genes from her.
                Alas, 23andMe does not currently "paint" the X. Considering its importance to obsessive genetic genealogists, I have been "hounding" the administrators and scientists there to complete the task (which is available to those who test through deCODEme). I was told that it may be completed by the fall, but who knows.

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                • #9
                  Originally posted by DKF View Post
                  Alas, 23andMe does not currently "paint" the X. Considering its importance to obsessive genetic genealogists, I have been "hounding" the administrators and scientists there to complete the task (which is available to those who test through deCODEme). I was told that it may be completed by the fall, but who knows.
                  Can you get the raw data files for X from 23andMe? Can anything be done with them on other programs? Such as was done with your DeCode data relative to Native American ancestry?

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                  • #10
                    Originally posted by tomcat View Post
                    Can you get the raw data files for X from 23andMe? Can anything be done with them on other programs? Such as was done with your DeCode data relative to Native American ancestry?
                    Go to "Raw Data" at the bottom of your home page and you can set the parameters to download. Since this is difficult for me I simply sent my entire raw data file in a zip format to Anders Palsen and Ben Moscia. The project we (Anders and I) worked on was entirely experimental and was completed since we both were curious about the findings seen in the decodeme browser in relation to a known genealogy.

                    There are at present no options for exploring the X in detail (mine was a one shot deal and via decodeme data). Any of the phasing programs such as PLINK, GERMLINE and BEAGLE could be used to analyze your X data in detail but as I understand it none of these are user friendly (I think that the whole 23andme dataset has to be flipped before proceeding). The learning curve is steep and the frustration level is bound to be high. I give Anders a lot of credit for his dogged determination to find answers. He has no intention at present to offer any commercial service. There is, however, absolutely no reason why the scientists at 23andme could not do the same thing. However they have yet to paint the X let alone doing more in depth sophisticated cross validated analyses.

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                    • #11
                      Originally posted by DKF View Post
                      ....
                      There is, however, absolutely no reason why the scientists at 23andme could not do the same thing. However they have yet to paint the X let alone doing more in depth sophisticated cross validated analyses.
                      Does X figure in the new feature, Relative Finding, now in beta? Or does 23andMe do absolutely NOTHING with X at present?

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                      • #12
                        Not speaking of the beta version here, but they do have the X in the Family Inheritance tool. Several folks have found half identical matches on the X and have then found distant family via paper trail connections.

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                        • #13
                          Originally posted by tomcat View Post
                          Does X figure in the new feature, Relative Finding, now in beta? Or does 23andMe do absolutely NOTHING with X at present?
                          It "appears" that in fact they do include the X in this analysis. One fellow has an X match on the p arm (about 6 Mb) with another fellow he is already sharing with. This is one segment only (one segment on the X is seen on the diagram of the comparison in the present family inheritance tool) and the percentage match is .13%. This is the same percent I have with the woman who is NA, and I have a 6 Mb Asian match on the X seen on decodeme. So while the X is not yet painted and can only be seen in diagramatic form if by chance or via a known family relationship you match someone on the X, the new tool offers a way around the "problem". I will need to contact the "5th cousin" and see if we do in fact match on the same 6 Mb segment of the X. It seems likely. I am testing my uncle who is only 3 meioses from our NA ancestor.

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                          • #14
                            Originally posted by DKF View Post
                            ... There is, however, absolutely no reason why the scientists at 23andme could not do the same thing. However they have yet to paint the X let alone doing more in depth sophisticated cross validated analyses.
                            What reasons does 23andMe give for their delay in painting X? It seems, given DeCode's analysis, there is sufficient worldwide data to make attributions of ancestry based on X markers.

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                            • #15
                              Originally posted by tomcat View Post
                              What reasons does 23andMe give for their delay in painting X? It seems, given DeCode's analysis, there is sufficient worldwide data to make attributions of ancestry based on X markers.
                              Sorry, I don't recall their rationale and I am at my home in Canada with no access to my notes in Cal. I expect that they did not anticipate the interest in the ancestry component and assumed that a cursory analysis would be more than adequate. They are well aware that they have to rethink their priorities but it will take time to get everything that we "need". They keep coming up with interesting features - but the downside is that they have continued to ignore upgrading the features already in place - such as Ancestry Painting.

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