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Chromosome Painting

The Chromosome Painting feature is an in-depth way of looking at your Ancestry Composition results. It shows a colorful representation of the 23 sets of chromosomes that make up your genome.

The chromosomes are shown in pairs and labeled with numbers (1 through 22) or the letters X; females will see two copies of the X chromosome, while men only see one copy of the X chromosome. This is because women inherit an X chromosome from each parent while men only inherit an X chromosome from their mothers. Instead of a second copy of the X chromosome, men inherit a Y chromosome from their fathers. The Y chromosome isn’t used to generate your Ancestry Composition report, so they aren’t shown in Chromosome Paintings.

In the Chromosome Painting, gray regions in chromosomes 13, 14, 15, 21, and 22 represent parts of the genome where 23andMe doesn’t test any markers because the DNA sequences in those regions are highly repetitive and hard to measure.

Go to your Ancestry Composition report (opens in a new tab).

 

Exploring Your Genetic Ancestry

Segment Color | Segment Length | Segment Location

Segment Color

In Chromosome Painting, your genome is “painted” with colors representing up to 31 different ancestries. You can hover over or click on the different ancestries in your Chromosome Painting to learn where they’re found in your genome.

The 31 Ancestry Composition populations are organized in a hierarchy, which reflects the genetic structure of global populations. For example, Britain and Ireland are part of Northwest Europe, which is part of Europe. To see this hierarchy in action, take a closer look at the Chromosome Painting below:

painting.png

Segment Length

The colors in your Chromosome Painting tell you about your Ancestry Composition, but you can learn even more by looking at the number and length of the DNA segments assigned to each ancestry. Everyone inherits half of their DNA from their mother and half from their father. When DNA is passed from parents to their offspring, the two chromosomes in each pair are randomly shuffled together in a process called recombination. This process breaks up long segments of a single ancestry into shorter segments. Sometimes very short segments of ancestry are lost during recombination and don’t get passed to the next generation. This is why ancestry from your distant ancestors only shows up in a few short segments of your genome, if at all.

The technical term for the genetic mixing of previously separate populations is admixture. If you have different DNA segments painted with different colors in your Chromosome Painting, those are evidence of admixture in your family history. Take a look at these two Chromosome Paintings side by side:

painting2.png

These Chromosome Paintings show very different genetic histories; the long, unbroken stretches of color on the left are evidence of recent admixture, while the short segments of different ancestries on the right suggest admixture many generations ago.

The Chromosome Painting on the left shows an example of ancestors from different European populations that started mixing together (at least in this family) only during the past two or three generations. The Chromosome painting on the right shows someone who identifies as Latino; his Native American (yellow), African (pink) and European (blue) ancestors probably started mixing with each other many generations ago.

In general, if your most recent ancestor from a population was very recent, you will have segments of that ancestry on more chromosomes, and those segments will be longer, than if your most recent ancestor was many generations ago.

Segment Location

Even if you are not connected with either of your parents through 23andMe, you may be able to learn a little bit about their ancestry by looking at the location of segments in your Chromosome Painting:

  • If you are male, you inherited all of the ancestry painted on your X chromosome from your mother. Because men and women inherit this chromosome differently, only certain ancestors could have contributed to your X chromosome. Note: To read the pedigree chart below, start with the blue square at the bottom of the chart (which represents you), and work your way through each generation to the top of the chart. Each ancestor is represented by either a circle or a square; female ancestors are represented by circles, and male ancestors are represented by squares. Ancestors that could have contributed to the X chromosome are highlighted in blue.

    Who_passed_along_your_X_chromosome_DNA_-_male_only.png

  • If you have the same ancestry painted in the same place on both copies of a chromosome, then you inherited the same ancestry from both of your parents in that region of your genome. Below you can see an example of someone who inherited British & Irish ancestry (dark blue) on both copies of chromosome 15.

    painting4.png

  • If your parents come from different genetic backgrounds, then you may be able to guess which chromosomes you inherited from which of your parents just by looking at the ancestries painted on each chromosome. Below you can see an example of someone with two parents from different genetic backgrounds. For technical reasons, this will work even better if you are connected with a parent* because our computational algorithm will be able to phase your raw data with more accuracy.

    painting3.png

*If you have a biological parent, son or daughter, who is also a 23andMe user, you can connect with them to improve the resolution of your Ancestry Composition results. Connecting with a parent will also reorganize your Chromosome Painting so that the top chromosome in each pair is the one you inherited from your mother, and the bottom chromosome is the one you inherited from your father.

 

Using Confidence Levels

If you’d like to explore at an even more advanced level, click on “Change confidence level” and move the slider that appears above your Chromosome Painting. You can explore the different views of your Chromosome Painting at different confidence levels, and you can also compare those different views to each other.

confidence_levels.png

The algorithm we use to calculate your Ancestry Composition analyzes one small piece of your DNA at a time. For each piece of your DNA, we calculate the probability of that piece coming from 31 different populations. The confidence slider on the Chromosome Painting allows you to explore our estimates of your genetic ancestry at different probability cutoffs. For example, if a segment of your DNA has a 55 percent chance of being Japanese, then that segment will be painted as Japanese at the 50 percent confidence level, but it will be painted with a more broad ancestry (either Broadly East Asian, Broadly East Asian & Native American, or Unassigned) at the 60 to 90 percent confidence levels.

For a detailed technical explanation of how we calculate your ancestry and paint your chromosomes, check out the Ancestry Composition Guide.

 

Common Questions

Do the chromosome numbers (1 through 22) mean anything?

In Chromosome Painting, your chromosomes are shown in pairs and are ordered by the length of the chromosome—chromosome 1 is the longest and chromosome 22 is the shortest. You received DNA on these chromosomes from all of your recent ancestors. Because the DNA on these chromosomes is randomly shuffled each generation, it is the the length and the number of segments from a particular ancestry, not the specific chromosome number (e.g. chromosome 1), that is informative about your ancestry. We recommend visiting Ancestry Timeline to learn how many generations ago you may have had a single ancestor who descended from a single population.


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