DNA – An Intro to Visual Phasing

Visual Phasing: the genetic genealogy phrase that generates fear in the heart of every genealogist.

Yep, I’ve been trying to tackle it. Here’s what I’ve learned, so far.

  1. What’s required in order to start using visual phasing will eliminate many. 3 siblings and uncle/aunt/1st cousin matches on both maternal and paternal sides. If you don’t have 2 siblings, the process is more difficult to an exponent. You may have to commit to finding more testers before you even start the process.
  2. Some have suggested using a Power Point slide for each chromosome. I found that it was too crowded and too confusing. If you like Excel spreadsheets, start there. Much easier. There’s a video link on the isogg.com/wiki/visual_phasing page using Excel. It’s great. There’s no audio and the spreadsheet isn’t in English, but if you’re familiar at all with Excel, easy peasy.
  3. The terminology can be confusing if you’re not a genetist. Sue Griffith at genealogyjunkie.net has some great tips. Including her image. Keep it handy.  
  4. There’s a lot of data to collect. I’d suggest working only one chromosome at a time. Blaine Bettinger suggests starting with the smaller chromosomes – 20, 21, 22. I agree. But, I’ve found that putting one chromosome per spreadsheet in Excel is helpful.
  5. Testing hypotheses. At some point in the process, you’re going to get very uncomfortable. No worries. This is science and you’re using the scientific method! You’re going to have to make a choice to assign a segment of DNA to a set of grandparents or to one grandparent. Just choose. It’s not the end of the world. If it doesn’t work. Revise your hypothesis and try again. You’ll get it.
  6. Along with #5, you’ll have to be really comfortable making assumptions. Those If/Then statements like, “If brother doesn’t match sister on this segment, then she inherited her DNA from the other set of grandparents.” Go slowly. I had my very logic-minded, data analyst of a husband check my work. So, ask a friend to help.

Remember, if something seems too hard, break it down into smaller pieces. Good luck.


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