What Are the Odds?NEW Read the FAQview in v2
This tool is designed to help you work out how one person, the "target", is related to a family group of people who have taken DNA tests. In particular, the tool is designed for when you have limited or no tree information about the target. The target may, for example, be an adoptee trying to work out how they fit into the family tree of a group of DNA matches. Or the target might be a new and unidentified DNA match who appears in your list.
To use the tool you will need to have the following on hand:
- A set of DNA matches who are all descended from the same ancestor (or couple) and from whom you suspect the target is also descended.
- The amount of DNA in centimorgans shared between the target person and each other person in the family group.
- Enough information about how members of the group are related to one another to build a basic family tree, including the common ancestor (or couple) from whom everyone in the family group is descended.
- Educated guesses (called "hypotheses") for where the target person might fit into the family tree.
Consider an example scenario in which Peter is trying to work out how he is related to Lisa, Mary, and Nora.
- Peter knows that Lisa, Mary, and Nora are all descended from Alice and Richard.
- Peter knows how much DNA he shares with Lisa, Mary, and Nora.
- Peter has built a family tree that connects Lisa, Mary, and Nora to one another through Alice and Richard.
With these pieces of information, Peter can use the tool to work out how he might be related to Lisa, Mary, and Nora (and, by extension, Alice and Richard). The steps are as follows.
- Build the tree in the tool, starting with Alice and Richard, then adding their children, grandchildren, etc.
- Add possible placements (hypotheses) for Peter into the tree.
- If there is a half-relationship, you can indicate this by hovering over the person and clicking 'Define half relationships'.
- Review the probability scores
You can also make notes and add them to this page, and can share a read-only version of your research.
Build the tree
- To start, click on "Most recent common ancestor or couple" and add the names of the person or couple you believe to be the ancestors shared by the target and their matches.
- Hover over this couple's names and click "add child" to add the name of the oldest child of the ancestor/couple.
- Repeat this process to build out the tree. You can add additional generations (grandchildren, great grandchildren, etc.) descended from the ancestor/couple in the same fashion.
- Should you want to add an earlier generation, hover over the name of the ancestor/couple and select "Add parent".
Add DNA match information
After you place a DNA match into the tree, hover over their name and click on "Enter match cM". Enter how many centimorgans are shared by the target person and the match. That position in the tree will change colour and show the shared DNA amount.
Enter known matches into the tree and enter the cM amount that the subject shares with them
- At GEDmatch, do a one-to-one comparison between the target person and the DNA match. Enter the value for "Total of segments > 7 cM =" into the match cM field.
- At AncestryDNA, click the green "View Match" button beside that DNA match in the target's match list. On the next page, click the little "i" inside the grey circle beside the Confidence Level. The popup will tell you the centimorgan amount.
- At MyHeritage, the shared centimorgan amount is visible in the target's match list. It is the number in parentheses beside the Shared DNA amount. Be sure to use the cM amount and not the percentage.
- At 23andMe, compare the target person to the DNA match in the chromosome browser to see the centimorgan amount (preferred method). If only the percent shared is available, multiply the percentage by 75.4 for a rough estimate of the shared cM amount.
- At FTDNA, select up to five matches to view in the chromosome browser. At the top of the browser, click on "View this data in a table". For each match, add up the centimorgan values that are greater than or equal to 7 cM. Ignore segments smaller than 7 cM. Use these adjusted totals for the matches in the tool.
Create a hypothesis by adding a child where you think the target person could fit into the tree. Hover over that child and select "Use as hypothesis". That position in the tree will have a coloured badge added and will be assigned a hypothesis number.
You must have at least two hypotheses for the tool to work.
Each hypothesis will be automatically labeled as Most Likely, Possible, Unlikely, or Ruled Out.
After you have added at least one match and one hypothesis, a badge will be added to each hypothesis in the tree. The badge will contain a score that reflects the likelihood of this hypothesis compared to the others you've defined. If the hypothesis is statistically possible, the badge will be shaded in green; if not, it will be shaded red. Below the tree, you will see the hypotheses listed with the most likely first.
If one hypothesis is at least 20 times greater than the next, this indicates significant statistical support for this hypothesis
Target name: Target
My research question is: Enter the question you are trying to answer here
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This is an example tree. Create a new tree by clicking here
You are viewing this tree in read-only mode. If you would like to make edits, please click Save and make a copy in your DNA Painter account first.
Hover over a person for options. Scroll to the right to see children.
You are currently in read only mode. If you make edits to this tree, they will not be saved. If you'd like to save it to your DNA Painter account, please sign in or register (free). You'll then see the option to save a copy of this tree.
Experimental: you can save an image of this tree. The results may vary according to your browser. For the best results, try to maximize the size of the window before clicking this button. This feature works best in the Chrome, Firefox and Safari browsers.
You can also download the data for this tree locally and load it back into the tool later (or send it to someone else so they can load it in).
To do this, click the button below.
After you've added matches and hypotheses to a tree, hypotheses will appear here.
This table shows the shared cM and probability data for each match.
For each hypothesis, the following is displayed:
- The genealogical relationship with each match based on the tree position of the hypothesis
(for example 3rd cousin)
- The probability that the amount of cM shared corresponds to this relationship
These individual probabilities are then used to calculate the combined odds ratio used for the score
The odds ratios are made by comparing all hypotheses that are considered possible and then determining the relative likelhood of each. For more information please see the FAQ.
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