Benefits of Visual Phasing

Visual Phasing is a technique whereby the DNA of siblings is assigned to each of the four grandparents. It is usually done with 3 siblings, though you can adapt the technique, as I did, with 2 siblings and a nephew.  As I mentioned in that post, I knew I want to try it as soon as I heard about it. I wasn’t really sure whether it would be helpful for me, but I was curious about the technique. While I was waiting for my sister’s and nephew’s results, I was chatting with a genealogist I know who referred to Visual Phasing as a “party trick”. She didn’t feel that there was much to be gained from doing it.

Having now mapped most of my chromosomes using Visual Phasing, I respectfully disagree – at least for me. Your mileage may vary.

Following are a couple of ways that Visual Phasing has helped me:

 1. I can easily identify whether a match is on a line of interest

The vast majority of my DNA matches are on my maternal grandmother’s side, as this line has deep Colonial American roots. As discussed in a previous post, I’m currently particularly interested in matches on my maternal grandfather’s side, as that’s where I’m attempting to break down a brick wall.

When I get a new match on GEDMatch, MyHeritage or FTDNA, I can quickly and easily figure out which side the match is on. For example, on GEDMatch, when I get a new match, I run a “Multi Kit Analysis”, select “Manual Kit Selection/Entry”, enter the new kit number in the 1st box, then compare it against my mother (FC), me, my sister (JK) and my nephew (RM):

Multi Kit Analysis

I click on Visualization Options, and select 2-D Chromosome Browser

Match Chr 11

For this match, I see that on Chromosome 11, she or he matches my mother (so I know it’s on my maternal line), matches R from 115 to 129, and matches me (L) from 119 to 129. I compare this to the phased chromosome:

Compare v11

As you can see by the the section outlined in red, this must be a Prowse match (purple). Since that’s my mother’s paternal side, the line I’m particularly interested in, I add this match to my spreadsheet as a match of interest. Doing this systematically has helped me develop a subset of matches to work with.

2. I have a much better understanding of how DNA is passed down.

When I first got my DNA results and started working with matches, there was a lot I didn’t quite get, like:

  • Why, with some matches, do I share the exact same amount as my mother, with some I share about half, and with others still I don’t share any at all?
  • Why do I match some people that my sister doesn’t, and vice versa?
  • How can my nephew share more with a person than I do, when he’s one generation farther back from the match than I am?

I have since learned that these are extremely common questions. I quickly learned that the stock answer is “because of the randomness of how DNA is inherited”. It was only when I started doing visual phasing that I really got it. It makes sense to me now. For example, with the match above my mother and my nephew (her grandson) share about the same amount with this person, I share a bit less, and J is not a match at all. And that’s totally normal.

It took seeing it for me to really understand.

I know that not everybody can do Visual Phasing. If you don’t have siblings to work with, you’re out of luck. But if you do, it’s worth considering. Of course, only you can decide if there’s a value to you – it depends on what you’re trying to accomplish.

For me, it was worth it. Plus, it’s kinda fun – but then again, spreadsheets and graphics make me happy.

What do you think? Party trick, or valuable tool in the genetic genealogy toolbox?

2 thoughts on “Benefits of Visual Phasing”

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