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Thread: New Parental Phasing

  1. #141
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    I really, really don't understand why Ancestry is now giving customers with two tested parents less value than they did previously. I say this because such customers already were being shown sides, well before Ancestry came up with SideViewTM.

    And why shouldn't they have been? After all, it's easy enough to determine. Every bit of a person's DNA has to come from one of two sources: either the person's father, or the person's mother. If both parents have been tested, one or the other ought to appear on every shared match their offspring have.

    In practice, that doesn't happen. For one thing, there's the 20 cM threshold to be on a shared match list. Sometimes, for various reasons -- often due to Timber, but not always -- someone will appear on the shared match of the child but not of the connecting parent. But this is not the most common scenario -- more often than not, the parent will appear on the relevant shared match list.

    And even if they don't, there's an easy way to determine if a parent shares at least 8.0 cM with their child's match, at least when all three profiles -- both parents and the child -- are in one account. Let's say I'm looking at my match GWS. This person happens to be my paternal 1st cousin, since my father and his mother are full siblings. GWS and I share 1,093 cM across 39 segments, with a longest segment of 108 cM.

    Now, I can call up a page showing GWS's account profile if I click on his name. At the top of that page I find the words "DNA relationship to", followed by my name. This is actually a drop down menu, and I can use it to show all the profiles in my account.

    Selecting my daughter's name, I can then see how much she shares with GWS. Obviously, he's her 1st cousin once removed, and the two of them share 547 cM across 20 segments, with a longest segment of 76 cM. I can do the same thing using my wife's name, but in that case I get the message that "[GWS] is either not a DNA match or has not taken a DNA test." Since I know he has taken the test, I also know that my wife is not a match.

    Of course, I really don't know that they don't share any DNA, but merely that they don't share enough for reporting purposes. That's now a minimum of 8.0 cM, or 6.0 cM for matches you protected from the purge.

    Anyway, what Ancestry has done is to now rely on SideViewTM alone, even for folks for whom a much better tool is available. Before the "new parental phasing", Ancestry already did that for people with tested parents.

    [EDIT] As an aside, going through my daughter's "Unidentified" matches and identifying them has really driven home the absolute unhelpfulness of Timber. For example, I just encountered my daughter's match "DD". DD and my daughter reportedly share 25 cM across 2 segments, but unweighted sharing is 30 cM.

    Neither parent is in the shared match list, but the first person in the list in on my wife's side. So, using the drop down list to switch to my wife's name, I see that she actually does share with DD, only it's reported as being 19 cM across 2 DNA segments. That puts it just under the threshold to be on a shared match list. But guess what unweighted sharing is: 30 cM.

    That means the only thing Timber has done here is keep a parent off their child's shared match list. Totally awesome, Ancestry ... not.
    Last edited by geebee; 11-23-2022 at 02:39 PM.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & another NA tribe, possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

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    Geebee, I agree with you - if both parents are tested then that should trump SideView, it really should simply default to straight-up parental phasing. After all, when both parents are tested and the child phased, this is the gold standard. In fact, SideView is supposed to be about 95% accurate (if I remember the figure accurately) when compared to dual parent phasing. I think the caveat being that the more close relatives you have, the better the phasing via SideView and the closer you get to 95% or beyond.

    I suppose one of the issues is that Ancestry is trying to get all customers on the same platform - in other words not to have multiple phasing approaches. It's a simplicity and consistency thing, I would guess. I also suppose that in the long run, especially as customers gradually acquire more and more matches, Ancestry is thinking that SideView will get better and better, so it's the way of the future. I was thinking that SideView does negatively impact their business/sales because part of the motivation to test parents was so that you could get phased, for matching purposes. However, I guess the bottom line is that (introducing SideView) ultimately results in more profits.

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  5. #143
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    Quote Originally Posted by Mr.G View Post
    Geebee, I agree with you - if both parents are tested then that should trump SideView, it really should simply default to straight-up parental phasing. After all, when both parents are tested and the child phased, this is the gold standard. In fact, SideView is supposed to be about 95% accurate (if I remember the figure accurately) when compared to dual parent phasing. I think the caveat being that the more close relatives you have, the better the phasing via SideView and the closer you get to 95% or beyond.

    I suppose one of the issues is that Ancestry is trying to get all customers on the same platform - in other words not to have multiple phasing approaches. It's a simplicity and consistency thing, I would guess. I also suppose that in the long run, especially as customers gradually acquire more and more matches, Ancestry is thinking that SideView will get better and better, so it's the way of the future. I was thinking that SideView does negatively impact their business/sales because part of the motivation to test parents was so that you could get phased, for matching purposes. However, I guess the bottom line is that (introducing SideView) ultimately results in more profits.
    Yeah, I'd imagine you're right -- Ancestry prefers being able to use just one approach for everyone. And at least in theory, you can do quite good phasing with no parents tested. For example, although they haven't tested at Ancestry, all five of my full siblings have tested at 23andMe. Our father has done so, too; but even if he hadn't, the six of us offspring probably collectively have nearly all of our parents' DNA. The first child covers half of the parental DNA, and (on average) each additional child covers half the remainder.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & another NA tribe, possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

  6. #144
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    Quote Originally Posted by geebee View Post
    Yeah, I'd imagine you're right -- Ancestry prefers being able to use just one approach for everyone. And at least in theory, you can do quite good phasing with no parents tested. For example, although they haven't tested at Ancestry, all five of my full siblings have tested at 23andMe. Our father has done so, too; but even if he hadn't, the six of us offspring probably collectively have nearly all of our parents' DNA. The first child covers half of the parental DNA, and (on average) each additional child covers half the remainder.
    Right, so I imagine between you and your siblings you most definitely have your parent's dna covered. Unfortunately, as I understand it, full siblings are not useful for phasing purposes because they have a combo of both your parents genes. What we really need are half siblings. So, five half siblings from your mother's side, and five half siblings from your father's side, that aught to cover it

  7. #145
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    Quote Originally Posted by Nqp15hhu View Post
    My most recent link is a GG uncle who immigrated in 1897, the closest match in that branch shares 245cms with me.

    Followed thereafter by a GGG uncle who immigrated in the 1870’s, the closest match in that branch shares 195cms with me.
    Yes, those are close. I don't have anyone who immigrated as recently as 1897, but my most recent English ancestor was born in 1851 and immigrated around 1872. He had a bunch of kids so I have connections to his descendants in the US, and I have some connections to his maternal grandmother's family who immigrated to Canada, but not many otherwise. I want to do a YDNA study so have tried to trace the UK family forward, but none of his brothers had sons, and his dad's brothers have incredibly common names so are hard to follow forward (their generation went from farms in Shropshire to bigger cities).
    Last edited by msmarjoribanks; 11-24-2022 at 09:41 AM.

  8. #146
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    Quote Originally Posted by Mr.G View Post
    Right, so I imagine between you and your siblings you most definitely have your parent's dna covered. Unfortunately, as I understand it, full siblings are not useful for phasing purposes because they have a combo of both your parents genes. What we really need are half siblings. So, five half siblings from your mother's side, and five half siblings from your father's side, that aught to cover it
    You're right that half siblings would probably make things clearer, although in this case we do also have my father's data. And five of my father's grandchildren have been tested -- my daughter; the son and daughter of one of my brothers; and the son and daughter of one of my sisters. But since this is at 23andMe it has limited usefulness at Ancestry. At least I can use this info to sometimes see when something doesn't quite make sense.

    I've found it very useful that there are some half sibling situations a couple of generations back from me. My paternal grandmother has around a dozen half siblings on her father's side -- she has no full siblings, and on her mother's side she's an only child. I have several half 2nd cousins that share descent from my paternal grandmother's father.

    In addition, my maternal grandmother has three older maternal half sisters (as well as an older full sister and a younger full brother). I have several half 2nd cousins that share descent from my maternal grandmother's mother.

    In both of these situations, it makes things "cleaner" with respect to our shared DNA, since that DNA was transmitted by just one person instead of two.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & another NA tribe, possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

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  10. #147
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    Quote Originally Posted by geebee View Post
    You're right that half siblings would probably make things clearer, although in this case we do also have my father's data. And five of my father's grandchildren have been tested -- my daughter; the son and daughter of one of my brothers; and the son and daughter of one of my sisters. But since this is at 23andMe it has limited usefulness at Ancestry. At least I can use this info to sometimes see when something doesn't quite make sense.

    I've found it very useful that there are some half sibling situations a couple of generations back from me. My paternal grandmother has around a dozen half siblings on her father's side -- she has no full siblings, and on her mother's side she's an only child. I have several half 2nd cousins that share descent from my paternal grandmother's father.

    In addition, my maternal grandmother has three older maternal half sisters (as well as an older full sister and a younger full brother). I have several half 2nd cousins that share descent from my maternal grandmother's mother.

    In both of these situations, it makes things "cleaner" with respect to our shared DNA, since that DNA was transmitted by just one person instead of two.
    EDIT: The difficulty in using full siblings for phasing is part of the reason that multiples help. Each parent passes on half of his or her DNA to each child, with the matter of which half being random. And each child also receives 23 chromosomes from each parent. Each one can recombined DNA from both grandparents on that side, or DNA from just one of the two.

    But basically, at any given location there are just four different possible sources of DNA for each sibling: maternal grandfather, maternal grandmother; paternal grandfather, and paternal grandmother. And there are essentially three different possibilities for a comparison of any given region of DNA between the siblings: they can not match at all; they can match on one side only; or they can match on both sides.

    Again, with enough siblings, it eventually should be possible to work out all four sets of chromosomes from the two parents -- even if you can't necessarily determine which two sets belong to which two parents.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & another NA tribe, possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

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  12. #148
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    Quote Originally Posted by geebee View Post
    EDIT: The difficulty in using full siblings for phasing is part of the reason that multiples help. Each parent passes on half of his or her DNA to each child, with the matter of which half being random. And each child also receives 23 chromosomes from each parent. Each one can recombined DNA from both grandparents on that side, or DNA from just one of the two.

    But basically, at any given location there are just four different possible sources of DNA for each sibling: maternal grandfather, maternal grandmother; paternal grandfather, and paternal grandmother. And there are essentially three different possibilities for a comparison of any given region of DNA between the siblings: they can not match at all; they can match on one side only; or they can match on both sides.

    Again, with enough siblings, it eventually should be possible to work out all four sets of chromosomes from the two parents -- even if you can't necessarily determine which two sets belong to which two parents.
    geebee and others ..I have been reading what all of you say and I don't seem to connect many places..Many of you have way more matches than I do.. I have almost 10,000 matches Paternal and the same maternal and almost 2,200 Unassigned.. NO parents alive.. However what geebee said here:" But basically, at any given location there are just four different possible sources of DNA for each sibling: maternal grandfather, maternal grandmother; paternal grandfather, and paternal grandmother. And there are essentially three different possibilities for a comparison of any given region of DNA between the siblings: they can not match at all; they can match on one side only; or they can match on both sides. " rings true for me..
    my Bio paternal grandfather had 4 other children mostly not alive today .. I match with one granddaughter and my Sister ( full sibling) and others and my Grandmother who I knew and loved had at least one child besides Dad who she did not raise.. I connect with her and the paternal sidelady as a 1/2 first cousin
    Everyone have a great Turkey Day for US folks
    Last edited by Kathlingram; 11-24-2022 at 04:28 PM.
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  14. #149
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    Quote Originally Posted by Loderingo View Post
    One thing to consider is that this match could be a close relation on your mother’s side but distant on your father’s. It would be helpful for both sides matches if Ancestry gave you the cm breakdown per side. Looking at my dad’s 4 both sides matches they are all 16-20 cm in total so presumably have only 8-10cm on each side. None of these have shared matches on either side.
    While this is a reasonable suggestion, so far in looking at my daughter's matches I have yet to find an instance in which an "Unassigned" match has proven to be on both sides.

    What I've been doing is going through my daughter's matches one-at-a-time to first look for either my wife or myself as a shared match. If neither of us is, I then go to the drop down menu in the match's profile and select first one of us, then the other. So far I've never had one or the other of us show up sharing at least as much unweighted sharing as our daughter does, or within a cM or so. But I've also not yet found an instance in which both of shared DNA with the match.

    Unfortunately, because I don't have any tested parents at Ancestry, I can't use this approach with RH. But, I will note that I've seen a few instances in which my daughter showed slightly more unweighted sharing with a match than the connected parent, or sometimes a longest segment which is longer by that margin. As I've said, this hasn't occurred very often, and it so far hasn't been by more than 1-2 cM. Even so, it shows that the phasing isn't perfect. A child simply cannot share more DNA with a match than the parent they inherited the match from, unless they're related on both sides.

    I have actually seen this with a couple of my matches -- not on my side, but theirs. I have one match who is both a 3rd cousin and a 3rd cousin once removed to me. It's because his father is my 2nd cousin once removed, and his mother is my 3rd cousin. I believe the parents are also 2nd cousins once removed to each other.

    Anyway, there is one location at which I share a segment with both of my match's parents, so that my match could have inherited it from either or both of them. But on my side, there's just my mother as the connecting parent.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & another NA tribe, possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

  15. #150
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    Looking at small matches in my daughter's profile, I've discovered that Ancestry has assigned sides to some matches that don't match either parent.

    I'm not just talking about the parent not being in the shared match list, but neither parent appears as a match even when selecting each parent in the match's profile. That means one of two things: the match to my daughter is bogus, or the amount of matching with the connecting parent was calculated at less than 8.0 cM and was therefore dropped. One thing that could cause a match to do this is Timber, even if the unweighted match is as high as or greater than 20.0 cM.

    I've also found one match -- so far -- that Ancestry lists as maternal, but should be both. Why? Because the match actually shares DNA with both parents: 10 cM with me (her dad), and 17 cM with her mother. So I changed the match to "both". But Ancestry is now showing "both" in red, and insists they think the match is only maternal. I've since found a second match just like this one, and I'd assume the two matches are probably closely related to each other.

    At 23andMe, three of my siblings actually share an 11 cM segment with my wife. I don't, but clearly if any of my siblings is related to her, so am I. (Ultimately, of course, everyone is related to everyone.) In this case, we might be 5th cousins or so, but our trees don't show any indication of anything that close. However, even though our parents are from different areas, there are a couple of places where one or another of our ancestors might have crossed paths.

    Anyway, Ancestry might be right about the side from a purely DNA standpoint. That is, my daughter's shared DNA with this person may be from only her mother. But, that isn't how relationships are actually determined. If a person is related to either parent, he or she is also related to the child -- regardless of whether they share any DNA. But I suppose that, yes, in strictly DNA matching terms the match may only be maternal.

    However, genetic genealogy is a means to an end -- generally, to determine whether two people are actually related. If you share DNA by descent, you're related. You're also related if either parent -- or any ancestor -- shares DNA with a particular individual. (And I'm related to 100% of the folks who share DNA with any of my siblings, even if I myself do not share DNA with the person.)

    I guess it depends on how you think about which side you're related to someone on. If Ancestry is considered only which parent you inherited DNA through, in some cases they should actually say "neither" -- because the parent does not clearly share the DNA (according to Ancestry's own reporting). But if they mean, on which side is the person related, then they're related on the side of which ever parent is also related to them, even if the child didn't inherit that specific segment.

    These matches might also be examples of incorrect phasing on Ancestry's part.
    Last edited by geebee; 11-26-2022 at 06:49 PM.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & another NA tribe, possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

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