Genetic distance?

[Devildog10111775]

I have quite a few matches after receiving my test results. On my left column it shows the genetic distance for all of them at "2." Could somebody clear up what exactly this means for me? Anything would be helpful.

Thanks,

Brandon S. Baker

[Jim Barrett]

More or Less!

If you take the differences in the values reported of each marker and add them up you will have, more or less, the genetic difference. In the case of markers with multiple markers the rule is a little different.

For a genetic distance of 2 you should find two markers that differ by 1 each for a total of 2 or one marker with a difference of 2.

[Devildog10111775]

So in essence, it is a very close match? I would assume that the term "close" is relevant to the number of markers compared too though. The more markers you test, the more room for mutation, while at the same time you can narrow down how close a relationship is.....am I on the right track here?

[Jim Barrett]

I would assume that the term "close" is relevant to the number of markers compared too though. The more markers you test, the more room for mutation, while at the same time you can narrow down how close a relationship is.....am I on the right track here?

Yes to everything above! A genetic distance of 2 on 12 markers wouldn't be considered close. A genetic distance of 2 on 67 markers would be considered close.

[Devildog10111775]

Thanks Jim! I was considering going back to school to get a second degree in genetics so I could interpret my results, but now I do t have to!

[Taed]

Thanks Jim! I was considering going back to school to get a second degree in genetics so I could interpret my results, but now I don't have to!

If you're the least bit serious, I recommend this free online course. I just completed it last week and it was worthwhile. It talks a lot about online DNA testing, so it definitely covers real-world topics.

https://www.udacity.com/course/bio110

[Bailey]

Genetic distance refers to the genetic divergence between species or between populations within a species. Smaller genetic distances indicate that the populations have more similar genes. This indicates that they are closely related

[chekwriter]

Genetic Distance - Do Twins make a difference? YDNA testing

Have noticed in some surname groups are several sets of twins.
Would a twin who have children, either singles or twins, too, would their DNA vary from generation to generation? There are a group of kits in the MILLS DNA project, and They all seem to have the same haplo group and STR i.d.
But the markers are slightly off, 1 or 2 on adjacent markers, from 12 out to 67 markers. The kit owners/researchers do NOT seem to be able to agree that they are actually related to one another.
Would the 'twin" concept have affect on their individual lines of descent?
Thank you
Patricia
cw

[Jim Barrett]

I would think their Y-DNA would vary from generation to generation just like anyone else's.

[Zaru]

????

I would think their Y-DNA would vary from generation to generation just like anyone else's.

Since when does Y-DNA vary from generation to generation? It doesn't. This is why the Y strand is such a reliable chromosome in determining relationships.

[Zaru]

Can you clarify what the genetic distance is at 67 markers?

Have noticed in some surname groups are several sets of twins.
Would a twin who have children, either singles or twins, too, would their DNA vary from generation to generation? There are a group of kits in the MILLS DNA project, and They all seem to have the same haplo group and STR i.d.
But the markers are slightly off, 1 or 2 on adjacent markers, from 12 out to 67 markers. The kit owners/researchers do NOT seem to be able to agree that they are actually related to one another.
Would the 'twin" concept have affect on their individual lines of descent?
Thank you
Patricia
cw

If it is only equal to two, share an identical surname, then they are most certainly kin.


Patricia-

[Pillar_of_fire]

I have quite a few matches after receiving my test results. On my left column it shows the genetic distance for all of them at "2." Could somebody clear up what exactly this means for me? Anything would be helpful.

there is a really good FAQ - Question 19
http://www.familytreedna.com/faq/answers.aspx?id=9#915

it also gives an example how it is calculated.

Then question 22 gives an answer how to interpret the genetic distance result in context of matching

http://www.familytreedna.com/faq/answers.aspx?id=9#919

[Jim Barrett]

Since when does Y-DNA vary from generation to generation? It doesn't. This is why the Y strand is such a reliable chromosome in determining relationships.

1) If it can't vary from generation to generation then we would ALL have the same Y-DNA.

2) If it doesn't vary from generation to generation then Bennett Greenspan must have been wrong when he told us, at the first conference in Houston, that he and his father had a genetic distance of one at 25 markers.

It is very common for father and son or brothers to have different Y-DNA. It is the fact that these changes do take place at a low rate that makes the Y-DNA test helpful.

I didn't say that it has to change from generation to generation, only that it can do so. Even at 111 markers we are only looking at a small part of the Y-DNA.

[Zaru]

1) If it can't vary from generation to generation then we would ALL have the same Y-DNA.

2) If it doesn't vary from generation to generation then Bennett Greenspan must have been wrong when he told us, at the first conference in Houston, that he and his father had a genetic distance of one at 25 markers.

It is very common for father and son or brothers to have different Y-DNA. It is the fact that these changes do take place at a low rate that makes the Y-DNA test helpful.

I didn't say that it has to change from generation to generation, only that it can do so. Even at 111 markers we are only looking at a small part of the Y-DNA.

You did say that it varies from generation to generation:

"I would think their Y-DNA would vary from generation to generation just like anyone else's."

You are misunderstanding mutation calculations. It is not common for father and sons to have different Y-DNA (by this I assume you mean distance as opposed to haplogroups).

According to the TMRCA calculator, one cannot have a gd=or >4 or 5 to be related within a genealogical time frame (1,000 years). According to this, given the calculus,a direct paternal lineage could have a mutation every 250-300 years (+/-), which obviously makes mutations uncommon.

To illustrate my point even further, one project that I manage has 15 "Y" cousins who claim the same most distant relative who was born in 1550. They are identical matches to each other with three exceptions, to which one is a mismatch of one, and two others are a gd=2. Hence, there have been no MORE than two mismatches over the course of 463 years.

So, while mutations can occur at anytime, their rates are much slower than what you are claiming.

[MMaddi]

You did say that it varies from generation to generation:

"I would think their Y-DNA would vary from generation to generation just like anyone else's."

You are misunderstanding mutation calculations. It is not common for father and sons to have different Y-DNA (by this I assume you mean distance as opposed to haplogroups).

According to the TMRCA calculator, one cannot have a gd=or >4 or 5 to be related within a genealogical time frame (1,000 years). According to this, given the calculus,a direct paternal lineage could have a mutation every 250-300 years (+/-), which obviously makes mutations uncommon.

To illustrate my point even further, one project that I manage has 15 "Y" cousins who claim the same most distant relative who was born in 1550. They are identical matches to each other with three exceptions, to which one is a mismatch of one, and two others are a gd=2. Hence, there have been no MORE than two mismatches over the course of 463 years.

So, while mutations can occur at anytime, their rates are much slower than what you are claiming.

I think you misinterpreted what he meant. I took his meaning to be that mutations are random, so a mutation can occur in any generation. And that is certainly true.

That's how mutations occur - in some (only a few generations) a son has a different count for an STR or has a new SNP that his father didn't have. In fact, with full yDNA sequencing results starting to come in, the estimate is now a new yDNA SNP occurs about every three generations on average in a paternal line.