DNA Testing - Y DNA

[Tricia_2]

Hi Craclyn 

Thanks.

Yes, the two Y-DNA tests that I have arranged for male relatives are specifically to look at those male lines, so that is fine. It's what I wanted.

The Ancestry test that I am hoping to take will be the autosomal DNA test, I think. It will be interesting to see what that reveals.

[Nick29]

You asked whether two men could have 'identical DNA'.   The answer to that is no.

They can, however have substiantially similar or identical Y-chromasomes.

This article explains it quite well....

http://chemgroups.northwestern.edu/lambert/dna/analysis.htm

[Tricia_2]

Hi again,

Yes, sorry, I was still referring to the Y-DNA.

Thanks for the link. That should prove to be useful

[Redroger]

As I understand it  autosomal DNA is inherited from both parents, a child will have 50% of its DNA from each parent, 25% from each grandparent, 12.5% from each great grandparent, diminishing by half in each subequent generation. Which suggests to me, that after the great grandparent stage autosomal DNA becomes of diminishing value, except perhaps in a family which is very inbred as a result of many 1st cousin marriages throughout history.

Are my thoughts right on this?

[andreabro]

I  have  done  this  test.   it  takes  some  time  to  get  your  head  around.  But  I  must  say  its  great  when  you  find a  name  in  common  say  250  years  back.   It  confirms  the  line   you are  following  is  correct.  I  have  also   found  further  ancestors .  often  you  will match  people  in common   and  this   gives  great  indications  of  names  you  should  look  at.

It  doesnt replace  the  paper  trail.  it  enhances  it  and  confirms.

[Tricia_2]

Sounds very exciting!

I must say that I am finding my results at FT DNA confusing.

I have read quite a bit on the subject ~ but clearly, not enough!

[andreabro]

Which  test,  and  how  long  have  you  had  the  results.

I played  around  with  them for a  bout  3  weeks  before  I started  looking.

[Tricia_2]

My brother had the Y-DNA 42 marker test done at DNA Heritage.
It was transferred to FT DNA, but has to be upgraded to be fully compared with their records.
I haven't done this, yet, as I am currently paying for anothey Y DNA test, on another relative.

Here's one example that I find bewildering ...

For one person who 'matched', I found three sets of results, regarding the chances of us having a common ancestor:

For Y-DNA 111 marker results ~ 94.99% within the past 8 generations

For Y-DNA 25 marker results ~ 29.79% within the past 8 generations

For Y-DNA 12 marker results ~ 20.09% within the past 8 generations

Why are the results so different for thje same questiion with the same person???
I just don't understand

[Redroger]

If 111 out of 111 markers match, then the probability of a relationship is far higher i.e.almost 95%, than if 25 out of 25 markers match, under 30%. A case of the more markers that match the better.