Talk: DNA test

The new text includes

Most of your DNA is autosomal/chromosomal DNA...Unfortunately for genealogists, because this DNA is "all mixed up" (recombined) from both parents, it cannot be isolated for genealogical information.

While this is true, as far as it goes, autosomal DNA can be used for genealogical purposes too. Its harder to do, but it is often used in a genealogical context when dealing with hereditary diseases. Those diseases have an hereditary basis because they are linked to a persons genetic code---and unless its a sex linked disease would be described as "autosomal". . As an example, in southwest Virginia there is a group of people known as the "Blue Fugates". They have a genetic mutation that leaves them with a dfinite blueish cast to their features. I understand that this mutation has been pinpointed to a specific individual living in SW VA about the time of the Revolution. There are many Fugates in the area that lack this mutation, and you can in many cases tell those descended from the original "Blue Fugate" by whether or not they share that trait, or in the case of recessives---whether they carry the gene. So, in cases such as this, you could in fact use autosomal DNA for purposes of genealogy. Bill 12:44, 5 September 2007 (UTC)

Ach! I see I errored in that example. The mutation in the Blue Fugate line is most likely sex linked---I don't believe it shows up in the distaff lines---only Fugate's. Still, the concept remains the same. Autosomal DNA testing does have a place in genealogy. Indeed, there are some advantages to it precisely because it is not sex linked. For example, you aren't limited to half of your family in autosomal testng. And some DNA testing services actually seem to specialize in this type of testing for genealogical purposes. Bill 14:53, 5 September 2007 (UTC)

There are two types of DNA that are useful for genealogists because they pass almost identically from one generation to the next. Y-DNA only passes from father to son, and mitochondrial DNA (mtDNA) only passes from mothers to her children. Most mt-DNA changes more slowly than Y-DNA over time, and so is more often used for anthropological studies of deep genealogy such as examining the ancient movements of peoples across continents.

That leaves the impression that YDNA is not useful for deep genealogy. In fact, its just about equally as useful. Again, using an example from SW VA, there was a recent test conducted of people said to have Melungeon ancestry. The Melungeons are a group of people said to have been in SW VA prior to the appearance of the first settlers. Their origin is something of a mystery (perhaps a self created one). The popular theory is that they are descendants of conquistador's in the Dom Pardo expedition through the southeast during the 16th century. Test this theory mtDNA was sampled from a goodly number of self described Melungeons. The conclusion of the researchers was that apart froma slightly higher percentage of Indian related mtDNA, they were indistinguishable from any other group of settlers in the area. Something of a downer for those looking for an answer to the question, and since then I've seen almost no activity on the subject. However---and I'm looking at this from afar, and do not have the original writings on the subject to examine, so I'm somewhat speaking off the top of my head---I really don't understand how a mtDNA test would prove anything. Exactly who did the researchers think these conquistadors were fathering children on? Clearly if there were any survivors of the Dom Pardo expedition that went native and reproduced, their children and descendants would be carrying Native American mtDNA, not Spanish or Portugese. If you wanted to test for traces of European heritage in these Melungeon descendants you want to be looking at YDNA, not mtDNA.

As far as the article is concerned, I'm giving those specific examples only to show that its a bit more complex than is currently described. The article is a good one to have here, but it needs a bit more depth in my opinion. Bill 12:44, 5 September 2007 (UTC)

I think we are in violent agreement. We need to have a simple page for folks to understand. We also need an in depth article that goes beyond the glosses that I made. If you look at the DNA pages on WP, they are not written in easy to understand terms. Too many new concepts are introduced and commonly understood information about DNA (such as the notion of "junk DNA"- though inaccurate is not leveraged.) Thorough explanations put a huge cognitive load on folks that just want to get the 2 minute version.

Specific points:

• Autosomal have a use? Of course it does. This is coverred in the catch-all "there are other tests..." The overall impression people should walk away with is that these aren't CSI type forensic tests where they can steal your identity/ know you will get diabetes etc. Worst case someone posts your DYS numbers is that some new cousin may find you. Previously, the article didn't even mention autosomal tests, though it is only type that folks are generally aware of. I'm saying- "here's what you know about (autosomal) It's not that, and that kind (scary from privacy standpoint) kind of DNA test is not what is being done. So don't freak out- that kind of stuff is generally useless to genealogists anyway, and here's why."
• Y-DNA useful for deep genealogy? Of course. There wouldn't be Y-Haplogroups without Y-DNA, and I actually do point out that UEDs occur in both Y-DNA and mtDNA. However, it is accurate to give the impression that mtDNA easier to use than Y-DNA for paleoanthropoligical uses. As Smolenyak explains, mtDNA has 16,569 base pairs, and they all have been sequenced. Y-DNA has 58 million and only about 23 million have been mapped. As I understand it, it is inherantly more difficult to use Y-DNA for such studies. Other differences:

compare	Y-Chromosome	mtDNA
Mutation rate	.002 per STR (avg- varies by STR)	.00001 per base
Longevity of Haplotype	Can last centuries	Pattern can last thousands of years
Present in hair shaft	No	Yes
Recovery from ancient remains	Very difficult	Possible, depending on condition
Where found	Male only	Males and Females

• Re Y-DNA for anthropological uses: "its just about equally as useful"? Well, actually no it isn't. And the above table gives an indication why.

-Mak 20:53, 5 September 2007 (UTC)

BTW- really, no one should be using the term "junk DNA" without qualifying it somehow. I have seen some sites refer to it as "non functional" DNA instead of Junk DNA, but it is just as false. There have been a lot of papers publised recently on different hitherto not understood functions such as the regulation of gene expression in response to environmental factors. This reaction to environmental factors could be an explanation of why some change/ regress very quickly.

I'll make two additional comments here:

1) I agree that theres a need for a clearly written article, accessible to the majority of people who might use this site. Simplifing a complex subject can lead to misunderstandings. The statement that Unfortunately for genealogists, because this DNA is "all mixed up" (recombined) from both parents, it cannot be isolated for genealogical information is not accurate. Autosomal DNA is and can be used for genealogical purposes.

Right. And some are pretty exciting. I was attempting to make a distinction with the ease of revealing the genealogical information such as father son, and mother daughter straight lines that can be quickly identified with y-Dna and mtDNA respectively. All information about one's ancestors provide clues of value to genealogists, so the statement is false. I would propose something having to do with the ease/ cost- benefit of these tests as opposed to the Autosomal tests. -Phlox- 21:40, 8 September 2007 (UTC)

Perhaps the text needs to revised so that it doesn't say it cannot be isolated for genealogical information. This is a significant subject to be writing an article about on this site. Such an article is needed, but I think there's a need to excercise care that what's here is not too casual as to be misleading. There's a fine line between "over-generalizing" and being "clear" for the majority of readers. Getting the right balance can be tricky. Bill 20:07, 9 September 2007 (UTC)

2) I suppose it depends a bit on what you want to consider "Deep Genealogy". If you are concerned with a period prior to perhaps 120,000 years ago, then perhaps mtDNA is more useful. However, most folks are, I think, going to be more interested in something a bit more recent than that. I believe the split between haplogroup A and B occurred something like 120,000 years ago, and the point of creation for a goodly number of haplogroups and types is in the 10,000 to 40,000 year range. While I'm sure there are some haplotypes of interest that originated fairly recently, the ones I've encountered are at several thousands of years. For those interested in such, a knowledge of the haplotype allows them to gain a feel for when their ancestors entered Europe, etc, and how they moved around. Whether that has any real bearing on their personal genealogy is another question, but one equally applicable to YDNA and mtDNA studies. Bill 14:55, 6 September 2007 (UTC)

TBD: Advanced subject/ maybe stuff for intro

• Glossary
• Quick factoids- what the tests are good for, what they aren't. Myths-common misconceptions.
• Enumeration of companies offering tests
• Enumeration of other types of tests
  • SNP (snips)
  • atDNA tests
    • BGA test (eg DNAPrint)
• FAQs
• How a modal haplotype signatures are determined for a particular ancestor.
• Mention of how quickly the field is moving (number of haplogroups discovered. Basically a statement how we really are just in the stone age.

-Mak 22:58, 5 September 2007 (UTC)