Lesson 4: Round Two — ICW, Trees & Segments
Start it in 5 minutes, let it run · What you'll have at the end: the relationship data that makes clustering possible.
So far you have a list of matches. This lesson adds the layer that turns a list into a network: who matches whom.
The three data types, in plain English
- ICW (In Common With) — for each match, which of your other matches they also share DNA with. This is the “shared matches” list you've seen on the testing sites, saved for every match at once. ICW is the raw material for clustering — tomorrow's lesson literally cannot run without it.
- Trees — the family trees your matches have posted, saved locally so you can search across all of them at once for surnames and ancestors (that's how the Gold tree tools in Lesson 8 find common ancestors).
- Segments — where on each chromosome you and a match share DNA (available on services that expose segment data). Segments power the Chromosome Matrix tool and triangulation work in Lesson 7.
Run the second pass
- Go to Gather and open the same service as Lesson 2.
- Turn on ICW, Trees, and Segments/Chromosome (where the service offers them — the options vary a little by service; see the Gather Overview).
- Keep the threshold at 30 cM for now — same matches as before, just deeper data about them.
- Start the gather. This pass takes longer than the matches pass; it's fine to leave it running while you do something else.
Tip: gathering in stages like this — matches first, relationships second, lower thresholds later — is the pattern experienced users follow for every new kit. The why and the trade-offs are covered in
Tips & Tactics.
✅ Do this now
- Open your service in Gather and turn on ICW, Trees, and Segments
- Run the gather at 30+ cM and let it finish (it's fine to walk away)
- When it's done, peek at Matches again — your matches now carry tree and shared-match data
With ICW data in your database, you're ready for the lesson everything so far has been building toward: your first cluster.