Term of the day: autosomes

Travel obligations and internet issues are going to be interfering with daily posts for at least some of the next 10 days to two weeks. So nobody will go into withdrawal, however, The Legal Genealogist offers…

The term of the day:


So… okay… we talk about the three types of DNA testing around here all the time on Sundays and one of those types is autosomal DNA testing — the type of DNA testing that can be done by men or women and that helps us find cousins in fairly recent generations.1

Which, of course, raises the question: just what exactly is autosomal DNA anyway? And the easy answer is, DNA contained in our autosomes. Which, of course, raises the additional question: just what exactly are the autosomes?

All of us as human beings have 23 pairs of chromosomes. All but one of them are referred to with numbers — chromosomes 1 through 22 to be precise. The last pair determines our sex. In that pair, women have two X chromosomes, one from our fathers and one from our mothers. Men have one X from their mothers and one Y from their fathers. (In case you didn’t notice, it’s that pesky Y chromosome that makes the guys guys.)

And… “an autosome is any of the numbered chromosomes, as opposed to the sex chromosomes.”2 In other words, chromosomes 1-22 are all autosomes.



  1. Judy G. Russell, “Autosomal DNA testing,” National Genealogical Society Magazine, October-December 2011, 38-43.
  2. Definitions: Autosome,” Human Genome Project Information (http://ghr.nlm.nih.gov : accessed 19 Oct 2013).
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2 Responses to Term of the day: autosomes

  1. Patricia Moore says:

    Best explanation ever! This is going in the binder of information I use when I’m explaining genealogical DNA testing to a potential swab subject!
    Thanks a bunch. You’re my favorite!

  2. Celia Lewis says:

    Ummmm. I knew that. I’m sure I did. Ummm. I think so… Well, I’m terribly clear now.

    Thank you Judy for being so very clear. Your use of visuals is so good! Like Patricia says up above: You’re my favourite! (canadian style)

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