Small DNA Segments 1

DNA Survey – Small DNA Segments

DNA Segments and their reliability for identifying DNA shared between descendants of a common ancestor are central to autosomal genetic genealogy. It is generally accepted that as the size of a DNA Segment decreases its likely reliability also decreases and the likelihood that it is a false positive increases. Thus, the subject of Small DNA Segments is both a controversial and an important topic.

As part of the DNA Survey series, my first survey question asked “A DNA Segment shared with a match is considered small when it is less than: 1 cM, 3 cM, 5 cM, 7 cM, 10 cM, 15 cM, I don’t know, or Other.”

On September 7th, 2017, I posted a survey to the Haplogroup FaceBook page.

When using DNA for genealogy, people talk about small DNA Segments. This survey is to find out what the average genealogist considers a small DNA Segment. There are no wrong or right answers; please give your opinion.

I also posted a message about the survey to the ISOGG DNA-Newbie Yahoo group.


Since then, the post has been shown to 4,340 people. The response rate in terms of likes, shares, and hides has been fairly typical of the FB page. There have been 214 clicks on the post. I would describe that as typical as well.

From those 214 clicks and clicks on the ISOGG DNA-Newbie post, 112 have completed the survey so far. These are used below for the first set of results.

Small DNA Segments - FB Post
Small DNA Segments – FB Post


Below are the results for n=112. While 7 cM is the most common response with 35.70% of the answers, all options are well represented.

Small DNA Segments Survey - First Results
Small DNA Segments Survey – First Results

Thank you to all who have responded so far. I plan to do the next update shortly past n=200, so please keep sharing with your friends and sending in your answers.

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