Visual Phasing: An Example (Part 5 of 5)

Five-Part Series on Visual Phasing:

In “Visual Phasing: An Example (Part 1),” we identified and labeled all of the recombination points in the three siblings, Susan, Brooke, and Felix. Then, in Part 2 of the series, we used the identified and labeled recombination points to assign segments of DNA to the four grandparents (the blue grandparent and grey grandparent pair, and the purple grandparent and green grandparent pair). In Part 3 of the series, we used cousin matching to identify the grandparental source of the chromosomal segments. And finally, in Part 4 of the series, we characterized my paternal chromosome.

After Part 3, we had the following for Brooke, Susan, and Felix:

step4g

Now that we have this information, let’s see if we can use that to explore new matches with Brooke, Susan, and Felix.

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Visual Phasing: An Example (Part 4 of 5)

Five-Part Series on Visual Phasing:

In “Visual Phasing: An Example (Part 1),” we identified and labeled all of the recombination points in the three siblings, Susan, Brooke, and Felix. Then, in Part 2 of the series, we used the identified and labeled recombination points to assign segments of DNA to the four grandparents (the blue grandparent and grey grandparent pair, and the purple grandparent and green grandparent pair). In Part 3 of the series, we used cousin matching to identify the grandparental source of the chromosomal segments. After Part 3, we had the following for Brooke, Susan, and Felix:

step4g

Since Felix is my father and Susan and Brooke are my aunts, I might be able to compare my DNA to my aunts in order to identify which of the segments I obtained from my father.

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Visual Phasing: An Example (Part 3 of 5)

Five-Part Series on Visual Phasing:

In “Visual Phasing: An Example (Part 1),” we identified and labeled all of the recombination points in the three siblings, Susan, Brooke, and Felix. Then, in Part 2 of the series, we used the identified and labeled recombination points to assign segments of DNA to the four grandparents (the blue grandparent and grey grandparent pair, and the purple grandparent and green grandparent pair):

step4b

But without more information, we don’t know to which grandparent each segment belongs.

Today, we’ll use cousin matching (defining “cousin” to mean anyone other than the siblings) to first identify the maternal pair of chromosomes, and the paternal pair of chromosomes. Hopefully, in the process, we’ll be able to assign the segments to each of the four grandparents, rather than just maternal/paternal.

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Visual Phasing: An Example (Part 2 of 5)

Five-Part Series on Visual Phasing:

In “Visual Phasing: An Example (Part I),” we identified and labeled all of the recombination points in the three siblings, Susan, Brooke, and Felix:

step-3a

In Part 2 of the series, we’ll use the identified and labeled the recombination points to assign segments of DNA to the four grandparents.

Step 3 – Fill in Chromosomes

The next step is to fill in the chromosomes using the identified recombination points. We’re going to start with the fully identical region shared by Susan and Brooke, shown in the red square in the next image. We can fill into both chromosomes for Susan and Brooke (the blue and purple segments):

step-3b

Each of the blue and purple segments is one of the following segments: (i) paternal grandfather; (ii) paternal grandmother; (iii) maternal grandfather; or (iv) maternal grandmother. We’ll try to figure out which is which later.

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Visual Phasing: An Example (Part 1 of 5)

Five-Part Series on Visual Phasing:

  • Part I – Explaining visual phasing and identifying/labeling recombination points (November 21, 2016)
  • Part II – Assigning segments of DNA (November 22, 2016)
  • Part III – Using cousin matches to identify which grandparent provided the segments
  • Part IV – Mapping my own chromosome using the visually phased paternal chromosomes
  • Part V – Using the mapped DNA with new matches

This weekend, I spoke at a meeting of the New England chapter of the Association of Professional Genealogists, and it was a wonderful group. One of my talks was about “Chromosome Mapping.” Unfortunately, since the talk was only an hour, we didn’t have time to discuss “Visual Phasing,” a chromosome mapping methodology. Instead, I promised to finish this blog post to explain the process. As I was writing, the blog post turned into a 5-part series!

Quick Summary

  • What is it? A method to assign segments of DNA to the test-taker’s four grandparents.
  • Why use it? To identify which grandparent gave the test-taker which segments of DNA (eliminating 75% of the family tree to search for MRCA).
  • What do you need? Autosomal DNA of three siblings uploaded to GEDmatch.

Visual Phasing

Visual Phasing is a process by which the DNA of three siblings is assigned to each of their four grandparents using identified recombination points, without requiring the testing of either the parents or grandparents. Although the process does not automatically reveal which segment belongs to which of the four grandparents, matching with cousins provides this identification as a further step of the process.

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