I've covered visual phasing, which usually needs at least three siblings or more to look at. And
people have asked about visual phasing with two people. I've already done a video on that. And
of course, somebody needs to ask the question: what about with half-siblings? Can we do visual
phasing with half-siblings? And, of course, the answer that is yes. There's some caveats, but yes,
you can do that. So let's go over visual phasing with half-siblings today. Howdy, welcome to Family
History Fanatics, where we love helping you climb your family tree and have fun along the way.
Now, as with visual phasing with two siblings, there are some caveats to visual phasing with
half-siblings. That's just because half-siblings have a unique feature that you don't see
in full siblings. And that is we need to remember always that half-siblings only share one parent.
So there's one parent in common. And then that half-sibling has a different parent from
their half-siblings. There's different ways that we could have half-siblings. So first off,
if we have three full siblings, a 3FS. Then we're just going to use our regular visual phasing
stuff. If, on the other hand, we have two full siblings plus a half-sibling, then
we are going to use two techniques. we're going to use a two-person visual phasing,
and we're going to use a half-person visual phasing. Now, this half-person visual phasing can
be one of two ways. The half-person visual phasing can be basically a half two visual phasing,
or it can be a half regular visual phasing. And you'll see here as I go through this a little bit.
And finally, if we have the other category. And that is going to be if we just have
two half-siblings. well, then we're going to use the half two-person visual phasing,
which is what I'm going to be showing you today. I've already made videos about
the visual phasing, and I've made videos about the two-person visual phasing.
Let me briefly talk about half visual phasing, and then we'll get
into the half two visual phasing technique. Going through, which is really just very similar to
the two-person visual phasing. Now for the half visual phasing, one thing that
we need to remember is that first principle I'm going to draw three pairs of chromosomes here
for a person A, B, and C. And C is our half-sibling. Now, if you remember from
our visual phasing principles, we have both maternal and paternal chromosomes. So
I'm going to say that this is a maternal chromosome. And that paternal chromosome is
here. And all of these share a mother because they share one parent. So this is a maternal
chromosome as well, which means that these other ones are going to be paternal chromosomes.
Now, these first two they share the same parent. So this paternal chromosome and this paternal
chromosome. while they may be different, they came from the same parent. But for our half-siblings,
their paternal chromosome is completely different. So what you see from this
is that a half-sibling visual phasing with at least three
really involves a couple of things. First off, for this chromosome, this is just
regular visual phasing because they all have the same parent. For the next part, though,
you'll notice that there's only two of these. And so this is going to be your two-person visual
phasing because they have the same father as well as the same mother. So we'll be able to use a
two-person technique on this, and that leaves us with our half-sibling. And, unfortunately,
one of the things that we have to realize here is without any other information,
we can't really do any visual phasing. On that last chromosome, we can identify it as
either paternal or maternal because we know who the common or uncommon parent is. But we can't
do any dividing up into segments for that because that chromosome is not actually being compared to
any other chromosome in order to identify recombination points. So you can see that with
three people, one of them being a half-sibling, you're just doing a combination of the full
visual phasing and of the two-person visual phasing, but with just one half-sibling and one,
I guess it's not really a full sibling they're both half-siblings. So you have two people.
what we have to do is we have to do really a modified version of our two-person phasings.
we only have two people, but we already know that we're only going to be able to do it for
one chromosome, and that's what we're going to be going over today. So step one, we need at least
two siblings' data uploaded to GEDmatch. In this case, we're going over how to do half-sibling
visual phasing with just two people. So our first principle again is that each chromosome
is separate and unrelated to the others, and this is really important with half-siblings
because one of those chromosomes. we're not going to be able to do a whole lot about it. So we're
going to do a side-by-side comparison, and with just two people, we're only getting really one set
of graphics here, and this is what it looks like. Now, if you've watched my other videos, you know
what these color regions mean, but we'll go over them really briefly. First off-color region one
solid green and blue represents a full match, but for half-siblings, there should be no full match.
So you really don't need to worry about this color region at all. If you do have solid green
as a full match with half-siblings, then they're also related in another way. Now the yellow and
green with some blue is the half-match regions. And the red that usually has some yellow and maybe
some green with black underneath is going to be a no-match region. where the color changes is our
recombination points and principle three, your full match cannot be adjacent to your no match.
we don't need to worry about this because we should not have any full match with half-siblings.
So our step three now is to go in and draw our recombination lines which we've drawn right there.
Now every chromosome, this is our fourth principle. Every chromosome
pair has a maternal and a paternal chromosome. Again this is important because they share one
parent in common and the other they don't. we're going to create two chromosomes for each person.
And now we get to principle number five. Each chromosome is made up of grandmother
and grandfather segments. So the whole goal of visual phasing is to divide up
the chromosomes to know what you receive from each one of your grandparents. But we have principle 5A
for half-siblings. One of these chromosomes is for unshared grandparents,
which means we can already do step 4A, and we can label one of these chromosomes as the unshared
parent chromosome. Now, in this case, what I've done is I have gone through, and since ultimately
we want to try to identify grandparents, I've put the two names of the grandparents for the unshared
set of grandparents in each one of these. So, person a has Brown and Townsend as grandparents.
And person B has Fey and Rey as grandparents. we're not going to be able to do anything else
with these chromosomes right now because we don't have anything else to match them to. Now,
if you happen to have another half-sibling that shared the same Fey Ray as person B, well,
then we could use them with this same technique to divide out how that Fey Ray chromosome is,
but for these really all we need to work with is the other chromosome. So on the principle 6, the
segments switch colors at recombination points for that person. Each recombination point is going to
be assigned to a single person. Rarely do you have recombination points in the same spot for multiple
people, and you rarely have them in the same spot for both of that pair of chromosomes. So we
want to color the largest no-match region that's because we don't have any fully matched regions.
A no-match region is going to tell us some information about both of the chromosomes. So here
we know that A and B are going to be different colors. And I've just done maroon and orange in
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Step six is we want to use our matches with known relationships to identify these segments. So let's
take a look at this match that is a Hankinson match. And it's not that big of a match,
but we're able to get a lot of information from it. And we can see from this match that
we have an overlap in this region. And we have overlap really right here that butts upright on
that recombination point well with this. Since we have this maroon overlapped, I know that
this has to be a Hankinson. So we're going to go through, and we're going to label that as
a Hankinson and because we can now extend these segments and add the new segments as needed. So,
in this case, we are going to move this Hankinson segment this way to cover all of this, and we're
going to add this as a Hankinson segment as well. And then, since we already know the Hankinson,
this is going to be our other one which is Anderson. So we've got one match so far, and we've
basically already gotten half of this chromosome identified. we can now identify the recombination
points, if there are any. And in this case, we do have one where Anderson changes to Hankinson. And
so we can label that as person B. Now that doesn't change anything as far as our next step, which
is to extend segments across recombination points because we've already extended that segment across
that recombination point. But if there were other places that you could, then this would be the time
to do it. Now we want to go on to our next step, which is to repeat steps six through nine, looking
at our matches with some other matches. well, I happen to have another Hankinson match, but
it only matches person A. And right here at the end, that means that it is Hankinson for person A,
and since this is a no match region, that's got to be Anderson for person B. So in just two matches,
remember when if you watch the video on visual phasing for two people, I actually use three
matches, but with two matches, I have one of my four recombination points identified.
I also have 75 of my segments assigned to a grandparent. So when we're dealing with just,
you know, the one chromosome like this because we've taken out the paternal chromosome,
we can get a lot of information with just a few matches really quickly. Now again, you're
going to do this for all 22 of your chromosomes, and this is just going to be that common parent
that you're solving for. If you happen to have another half-sibling that has the other parent,
the uncommon parent, in common, then you can solve for that other one, but without that,
you're really just going to have to use DNA painting with some matches on that side to
try to figure out where those overall segments would be. So visual phasing is possible with
half-siblings as well as with just two people. you're just applying some different techniques
to change the process up based on the information that you have. Now,
if you'd like to see a different way to do visual phasing that I call segment phasing,
then check out this video up on top here. But if you want to learn something else about DNA,
then there's this video down below. I think we're gonna have sneezes during the Livestream today.