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What the Heck is “X”?
Have you ever gotten a DNA test? A couple of years ago I have been gifted a DNA test on 23andme and when I received the ancestry report – I was a bit confused, to say the least. For the “Ancestry Composition” you see numbers and the letter “X” with rows of red lines, some small, some long. But there is no explanation. Just lines. What do these mean?? And what the heck is “X”?
According to 23andMe,
These are your chromosomes; we’ve painted them with your Ancestry Composition results. The first 22 are called autosomes and come in pairs of two, each represented by one of the colored horizontal lines in the graphic below. Chromosomes have different lengths, and are named 1 through 22, when sorted by size (scientists are not very creative). Lastly, we also look at ancestry on your X chromosome: two copies like the autosomes if you are female, and only one copy if you’re male (that you got from mom).
Even with that explanation, I am still rubbing my head and decided to stay focused on the Health Reports and DNA Relatives portions that 23andMe provides.
Thankfully though, Ancestry.com provides a much more detailed explanation of what X-DNA is.
X-DNA refers to the DNA found on one of the sex chromosomes, the X chromosome. The other sex chromosome is the Y chromosome. Typically, most people get one X chromosome from their biological mother, and an X or a Y chromosome from their biological father.
See their website here for more details about X-DNA.
How Helpful is the X-DNA in Identifying Relatives?
The two main ways to predict a relationship with a DNA relative are the total cM of matched segments and the size of the longest matching segment.
The X DNA comes in handy when you have a large matching segment with a DNA relative. If either you or the relative is male, you can deduce that the relationship is on the maternal line since (for a biological male) an X chromosome can only be inherited through the mother.
I personally found a 2nd or 3rd cousin on 23andMe and due to our X-DNA segments matching, we are able to confidently say the connection is a 2nd great-grandparent on our maternal lines. So, yes, knowing your X DNA connections can be very helpful in narrowing down connections.
What is the Best DNA Testing Site?
When I got my 23andMe test, it was lauded as the best for getting genetic testing for those who’ve been adopted and don’t know their health background. Since my test was done, the interest has soared and so has the price. At the time of publishing, 23andMe is offering a $50 off discount for Mothers’ Day.
Now, other websites like ancestry.com are offering health test options too. [At the time of publishing, they are not offering any Mothers’ Day discounts.]
The biggest bonus with using Ancestry.com versus 23andMe is the opportunity to include your DNA ancestors and cousins in your family tree that you’ve been working on (subscription required).
Do note that BOTH Ancestry and 23andMe will NOT allow you to upload DNA files from any other site onto their server. If you get tested on Ancestry and decide to check for DNA relatives on 23andMe you would have to be tested all over again.
And for those of my beautiful readers in the United Kingdom – you’ll want to check out Living DNA.
Result: So if you are American and looking to find DNA relatives, the best bet will be Ancestry.com, and if you are looking for more genetics testing or relatives who’re from East Asia you’ll likely want to go and use 23andMe.com.
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I hope this has been helpful! Have you had your DNA tested? Learn anything interesting?