HomeDNAChromosome Portray at Ancestry – The DNA Geek

Chromosome Portray at Ancestry – The DNA Geek

AncestryDNA not too long ago launched a brand new characteristic that maps your ethnicities onto your particular person chromosomes.  This beta chromosome painter will be discovered within the “DNA Story” tab.


The chromosome painter builds on know-how that Ancestry’s scientists launched with SideView™.  SideView™ is a technological advance that may apportion your ethnicity estimates to the contributions from every guardian.  It does this by evaluating your DNA to that of your matches.

Consider it this manner:  if each of your dad and mom have examined, all of the system has to do is evaluate your DNA to theirs to find out which copy of chromosome 1—we’ve two copies of every chromosome—got here from Mother and which got here from Dad.  The identical with every of the opposite chromosomes.  Even when just one guardian has examined, the chromosomes will be sorted by technique of elimination.  This sorting course of is named phasing.

But when neither guardian has examined, issues get trickier.  Contemplate a match who shares a single DNA phase of 25 cM with you.  The algorithm will have the ability to section that small portion of your DNA into Mother or father 1 and Mother or father 2, but it surely gained’t have the ability to inform which guardian is which, nor will it have any perception into the remainder of that chromosome or any of the others, for that matter.

Now think about a primary cousin match, just like the one proven right here.  These two cousins share about 1,100 cM throughout 34 segments, with no less than one phase on each chromosome besides numbers 14 & 21 and the X chromosome.  The algorithm nonetheless doesn’t know whether or not this can be a maternal cousin or a paternal cousin, however it could actually no less than conclude that each one 34 of these segments got here from the identical guardian.  We’ll name this Mother or father 1.  By technique of elimination, the complementary segments on every chromosome will need to have come from Mother or father 2.

One other first cousin on this aspect is probably going so as to add an extra 600 cM or so to our Mother or father 1 phasing.  The algorithm is aware of the segments got here from the identical aspect as a result of the 2 cousins may also match each other.  (This phasing algorithm will be misled by endogamy.)

Extra distant cousins may help, too, particularly in the event that they share segments on two or extra chromosomes.  The algorithm will section your DNA utilizing cousins on each side, typically assigning DNA areas based mostly on a constructive phase match and typically by elimination.

With a big sufficient database, the strategy ought to have the ability to section all or nearly your entire genome.  AncestryDNA is positioned to profit from this know-how, as a result of they’ve the biggest database of the family tree firms, greater than 22 million folks as of June 2022.  Examine that with the following largest database, 23andMe, which has roughly 13 million genotyped prospects.

As soon as the DNA is assigned to Mother or father 1 and Mother or father 2, the ethnicity estimates will be divided up accordingly.


Chromosome Portray

Which brings us again to the brand new chromosome portray characteristic.  All the main family tree DNA firms estimate ethnicity piece-by-piece alongside the chromosomes, and each 23andMe and FamilyTreeDNA provide chromosome work.  These are visible representations of the place alongside your chromosomes every ethnicity is discovered.

AncestryDNA is now displaying us the identical data, however with the additional advantage of sorting the chromosomes by Mother or father 1 and Mother or father 2.  Even when neither guardian has examined there.

To see your chromosome portray, click the blue “View Breakdown” button beneath the SideView™ circle (see first picture above), scroll down, and click on “Discover now” within the Chromosome painter panel.  Sure, it’s a bit hidden; I hope they’ll make this characteristic simpler to seek out as soon as it’s out of the introductory beta section.

Right here’s mine:

It’s fairly neat!  You’ll be able to see that considered one of my dad and mom is usually Germanic and Irish (teal and medium blue segments) whereas the opposite is usually French (inexperienced).  This aligns properly with the household histories of my German–Irish father and Cajun mom.

These of you into DNA Painter shall be glad to know that the inimitable Jonny Perl has already created a approach to import the Ancestry ethnicity portray into his instruments!


A Deeper Evaluation

I do have some critiques, although.  The primary is that my phase assignments from AncestryDNA and 23andMe aren’t significantly related, as you possibly can see.

For this comparability, I imported segments from each firms into separate DNA Painter chromosome maps and tweaked the colours to be related.  In each maps, my paternal chromosome is above my maternal one.

At first look, the obvious distinction is that AncestryDNA favors strong chromosomes of a single ethnicity whereas 23andMe reveals extra variation throughout most chromosomes.  This was a bit stunning provided that AncestryDNA has a extra fine-grained reference panel (77 areas) than 23andMe (44 areas), so I’d anticipate AncestryDNA to have the ability to give me extra precision.

After all, which firm is extra appropriate is an open query.  On this entrance, I’m inclined to imagine 23andMe.  Why?  Contemplate my paternal chromosomes.  Solely two of them (chromosomes 3 & 4) present any ethnic mixing.  My father’s mom was 100% German whereas my grandfather was about 60% Irish and 40% German.  It’s unlikely that the chromosomes I inherited from my father can be all one or the opposite.

What’s extra, AncestryDNA reveals chromosomes 9, 11, and 20 as all Scottish and chromosome 15 as all Sweden & Danish.  I’ve no identified ancestry from both area, and any unknown heritage needs to be in segments a lot smaller than a complete chromosome.

Then there’s the Spanish phase on my maternal chromosome 8 (purple).

Roughly 2,000 Canary Islanders settled in southern Louisiana between 1778 and 1783, together with a few of my ancestors.  Though an imperfect proxy, my tree suggests I’m about 5.5% Spanish.  But, Ancestry finds just one phase making up 1% of my genome.  By comparability, 23andMe estimates me at 9.7% Spanish & Portuguese.

What’s extra, that is my mother’s chromosome 8 at AncestryDNA:

And right here’s the Spanish & Portuguese estimate for me from 23andMe on chr 8:

The Spanish fragments simply barely overlap!

I believe the 2 points are associated, that Ancestry’s ethnicity algorithm penalizes a swap from one ethnicity to a different, inflicting chromosomes to be assigned a uniform ethnicity after they shouldn’t be and impacting the place the true breaks ought to happen.


The Good Information

Happily, the chromosome portray remains to be a beta characteristic, which means that AncestryDNA‘s scientists and programmers are nonetheless engaged on it.  And it’s an excellent addition!  AncestryDNA not too long ago introduced that their annual ethnicity replace will occur within the coming weeks.  I’m wanting ahead to seeing how the chromosome portray characteristic improves!



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