Cousin - Wikipedia
The 23andMe DNA Relatives feature uses patterns of DNA sharing to estimate relationships. Cousin relationship, Probability of detecting Aunt / Uncle Niece . DNA Shared Between Relatives The chart also ignores relatively rare phenomenon such as the elusive double cousin. These relationships. A chart of relationships and ranges of relatedness at the DNA level (ISOGG The 16% is actually between an uncle/nephew and first cousins.
And my example is with DNA that fits closely with the average amount these relatives share. Yours is even trickier. Or of course neither could be right too. This is why it is sometimes important to include other data or relatives to confirm a relationship. This is pretty much the only relationship that is almost always an exact number like this. Click here for one of the rare exceptions. Other relationships will share an amount of DNA around an average amount.
And the further you get away from a relative, the wider that range can be.
But they could share a bit more than this or a bit less. And how it is passed down. It is split up into 23 pairs called chromosomes. One set of 23 comes from mom and one set from dad for a total of 46 chromosomes.
When we have kids, we pass one from each pair down to each of them. This is why we share half our DNA with our moms and half with our dads.
Once you get past mom and dad, though, things get a little less precise. This has to do with something that happens before we pass our DNA down to our kids—recombination.
Recombination is when DNA is swapped between two chromosomes in a pair. She gives you a mix of the two. Same thing with dad. It is this mixing that can cause the wide range of shared DNA between similar relatives. Remember, what I am describing happens for all 23 pairs.
Parent-child pairs share between Blaine Bettinger has been collecting statistics from the genetic genealogy community on the number of shared centiMorgans for known genealogical relationships as part of his shared cM project. The chart below is a visualisation of the range of shared centiMorgans based on data supplied to the project based on over 25, known relationships.
You are free to share and use the information for non-commercial purposes, as long as you give proper attribution and release anything you create under the same licence. Additional information including histograms and the breakdown of companies is provided in the PDF download.
What Are Double Cousins? | Blog | Famicity
Data is still being collected for the project and you can add your own statistics using this form on GoogleDocs. Jonny Perl has created a tool based on the data from the Shared cMs project which allows the user to enter the total cMs shared and get a report on the number of possible relationships. The tool can be found on the DNA Painter website. Tim Janzen has created three charts that provide statistical information in various categories.
The charts provide statistics on close relatives, distant endogamous relatives and distant non-endogamous relatives.
The charts are organized by the degree of relationship, with the most closely related people parents and children, full siblings being listed at the top and more distant cousins being listed at the bottom. The statistics are based on information from real people who have been tested by 23andMe and Family Tree DNA and who have a known genealogical relationship to someone else who has also been tested by the same company.What's a Second Cousin vs. a First Cousin Once-Removed?
The charts also include information on the median and the average number of shared cMs for people who are related to each other from the first cousin once removed level of relationship to the 5th cousin level of relationship. The charts can be downloaded from Anabaptist Genetic Genealogy website. Tim Janzen has also compiled a chart showing the probability of a given genealogical relationship for each cM threshold going up in one cM increments starting at 6 cMs and going up cMs.
The chart may be downloaded as an Excel file from this link: Relationship prediction chart based on shared autosomal DNA.
This chart applies to non-endogamous populations. When using the chart to predict relationship from Family Finder data you will need to remove the data for all segments under 4 or 5 cMs.
For details see the guest blog post by Karin Corbeil on the DNAeXplained blog on Demystifying Ancestry's relationship predictions inspires new relationship estimator tool.