I recently attended an all day genealogy seminar. Overall, the day was a success. After lunch, I intended to listen to a lecture on the importance of encouraging family members to preserve their history for future generations. Unfortunately, the speaker didn’t show up. At that point my choices were limited, so I chose to attend a lecture on beginning DNA research. Ordinarily, I wouldn’t have bothered, but I am curious to see how other speakers handle the topic. The speaker was very entertaining, and he covered the basics. However, I was extremely dismayed to hear him treat mtDNA and the X-chromosome as BASICALLY THE SAME THING. He couldn’t have been more wrong! And he did an extreme disservice to the audience, who were mostly inexperienced newcomers who didn’t know the difference between y-DNA, mt-DNA, and autosomal DNA, let alone understand the difference between the X-chromosome and mt-DNA.
When genetic genealogists talk about autosomal testing, they are referring to the twenty-two pairs of autosomes that make up the human roadmap. Currently, the autosomal DNA test is the most widely administered DNA test for genetic genealogy. In addition to the twenty-two autosomes, all humans have a pair of sex chromosomes, also known as chromosome pair twenty-three. A female receives two X-chromosomes, one from each of her parents. A male receives one X-chromosome from his mother, and one Y-chromosome from his father. The Y-chromosome makes a baby a male, and is only inherited from the male parent. Sadly, Henry VIII didn’t know this in the 16th century and blamed his wives for the lack of a male heir. The Y-chromosome test was the first DNA test made available to genealogists well over a decade ago. Only males can take this test. When a person takes an autosomal DNA test, their X-chromosome(s) is/are included in the test.
Because of the unique way that the X-chromosome is passed down, hopscotching it’s way over male descendants, tracing X-chromosome matches can rewarding. [On a side note – because the X-chromosome sometimes skips generations, it often experiences less recombination. In practice, this means that a cousin match can actually be farther back than predicted.] A perfect example is my son’s X-chromosome. He only inherited one…from me. It turns out that he did not receive a recombined X-chromosome. Typically, part of the X-chromosome of my father and part of the X-chromosome of my mother would have been broken apart into segments and then pieced back together to create one whole X-chromosome for my son. What my son received was the entire X-chromosome from my father, without any recombination. And where did my father receive his X-chromosome? From his mother (and in case if you have been following my blog for the last five years, you are very familiar with her!), Gladys (Foster) Yegerlehner. So my son is the recipient of an entire chromosome that he received directly, un-recombined, from a single great grandmother. And doing the math, this specific X-chromosome has been around for three generations. If my son has a daughter, it will survive for another generation as well.
There are some great charts available to help keep track of one’s X-chromosome inheritance. Below is a female X-chromosome chart with the data filled in from my family tree. I only filled in the ancestors who would have potentially provided me with a segment of their X-chromosome.
Resources for X-chromosome Charts:
Blaine Bettinger has male and female charts available on his website. Don’t forget to read his in-depth blog posts about the subject as well.
http://thegeneticgenealogist.com/2009/01/12/more-x-chromosome-charts/
Debbie Parker Wayne has made several charts available on the publication page of her website.
http://debbiewayne.com/pubs.php#quickref
Sue Griffith has versions of X-chromosome charts on her website:
http://www.genealogyjunkie.net/downloads.html
©2017 Deborah Sweeney
Post originally found: https://genealogylady.net/2017/04/25/down-the-dna-rabbit-hole-x-chromosome/
“The Y-chromosome makes a baby a male, and is only inherited from the male parent. Sadly, Henry VIII didn’t know this in the 16th century and blamed his wives for the lack of a male heir.” Fascinating stuff!
Too bad about the instructor! Great post. 🙂
Sometimes I feel like I need a DNA super hero cloak to fly around and help prevent misinformation. 😁
🙂
i would like to talk with you about my dna if i could. email me alesiablogs@hotmail.com
I am in Seattle so you will have to give me a good time to call Always enjoy your blog so will be good to talk with you when you have time thx, Alesia
I’ve done mine and my moms on Ancestry- it takes time to fully understand it. Thanks for the links / I do need to get a better grasp on how it all works.
I hope my article helped! Understanding DNA research does has a bit of a curve to it, but it’s a great tool once you get a handle on it.
Thank you for reading!
Deborah
This is an excellent article! I find this confusion between X-DNA and mtDNA constantly from newbies to those with some experience spreading more confusion to newbies who are already overwhelmed.
Here’s a link to a video that I created on this very subject, because something had to be done to clear up the confusion. Looks like I’m not the only one on a mission to do so 😉
Thanks for the video link! I think if we keep teaching the differences, the knowledge will passed on!
Thank you for stopping by my blog,
Deborah