13 votes
Accepted

Generational Loss of Data with DNA Testing

(Note: I did not view the updated part of the question before writing this answer, so my original answer does not address the specific scenario added in the update. See the section below the dividing ...
  • 24.4k
10 votes
Accepted

Where can I find a centiMorgans calculator?

There is a service to turn a physical chromosome position (measured in base pairs, "bp") into a linkage position (measured in centiMorgans, "cM") here: http://compgen.rutgers.edu/map_interpolator....
  • 3,857
10 votes

Why no DNA match with possible seventh cousin?

The amount of autosomal DNA shared by 6th or 7th cousins is quite small. Some will share no detectable DNA. The latest data of the Shared cM Project shows that seventh cousins share between 0 and 57 ...
  • 18.6k
10 votes
Accepted

How to narrow down the best DNA donors in a large family?

I think you just posted that question to make all other genealogists envious of what you have to work with. :-) But seriously, yes, there are some things you should do and do as soon as possible (i.e....
  • 16.5k
10 votes
Accepted

Explaining major discrepancy in genomic position between Gedmatch and MyHeritage?

It looks like this may be due to a difference in the Genome Builds (https://en.wikipedia.org/wiki/Reference_genome#Human_reference_genome) used between the two tools. GEDMatch reports that they ...
10 votes

Sharing 52% DNA with mother

This could also be explained if the parents share DNA. If you took the same test with your father and it also was > 50%, it could indicate they are distantly related. A single shared chromosome ...
  • 201
9 votes

Finding haplogroup through raw DNA data?

I obtained my Y-DNA haplogroup from my AncestryDNA raw DNA file using the first method detailed in this link: https://www.geneticgenealogist.net/2016/01/how-to-get-ydna-haplogroup-from.html In short,...
9 votes
Accepted

How to get an elderly person to provide saliva sample for DNA?

I had my 93 year old uncle take a test after he agreed to do it. I did not feel comfortable asking him to do it, or for me to attempt to administer it. My uncle was at a nursing home. I asked one ...
  • 16.5k
9 votes

Does having child of DNA tested parent help find parent's DNA ancestors?

I think the prior answers are either misleading or wrong, and people should not miss out on the opportunity to get great DNA information because they were discouraged by those answers. If you have ...
8 votes
Accepted

How long do results typically take for AncestryDNA test?

Each entities lab's time are different and it also depends on what test you perform. This is due to them queuing up tests into large scale batches to use shared labs since many do not have their own ...
  • 5,531
8 votes

Is this adopted DNA match my niece or half sibling?

The adoptee is very likely your niece, specifically the half-sibling of the niece you have also tested. The relationship could be diagrammed as follows: The X-DNA is key to determining this ...
  • 18.6k
8 votes

Predicted percentages of shared DNA for DNA tests of half-siblings?

The ISOGG Wiki's article on Autosomal DNA statistics explains the concepts in the previous answer in much more detail -- and includes links to the AncestryDNA white paper that explains Ancestry's ...
  • 24.4k
8 votes

Can the amount of saliva affect how many centiMorgans are shared between 1st cousins?

Absolutely not. The amount of saliva is a factor in whether or not you get DNA results at all. If you have them, that's it. While there is such a thing as "partial results" it's because you need ...
7 votes
Accepted

My Father passed away - next test(s) on what remains of his DNA sample?

The short answer is being you have completed a very basic Y test and you should have met ftDNA's internal requirements of first doing a Y-## test before being able to order a BigY test and even if ...
  • 5,531
7 votes

Interpreting X DNA?

One of my favorite math teachers in high school told us that whenever we got stumped, we should draw a picture to get a better definition of what the problem was. Here's a recent (12 June 2015) ...
  • 24.4k
7 votes

How to interpret a reasonable X DNA Match, but no shared cM Autosomal result on GEDMatch?

For a person who is related somewhat distantly (say, third cousin or farther), it is common to share only a single DNA segment (if any). The shared segment may be located on an autosome or, if the ...
  • 3,857
7 votes

Is a half-sibling match on AncestryDNA reliable, or is more testing needed?

The result should be reliable in that it shows a close relationship. As shown on the Autosomal DNA statistics page on the ISOGG Wiki, the relationship is almost certainly one of these: one of you is ...
  • 3,857
7 votes
Accepted

What does 'DD' mean in a name on GEDmatch.com?

The "DD"-prefix simply means that they're a member of the Facebook group "DNA Detectives". It's a Facebook group for people who use DNA genealogy to track down family members. If you're on Facebook, ...
  • 5,166
7 votes

Unknown 1st cousin match who shares matches with both grandparents

You're starting off with a doozy of a match. Yep, something's going on here. Let's start with the shared cM project. Looking at the total cM match only, your possibilities for a 1,193 cM match ...
7 votes

2nd cousins. One 4%, one 8%?

DNA inheritance is very random in terms of how much DNA you get from each ancestor, due to genetic recombination. This basically means that although you get close to exactly 50% of your autosomal DNA ...
  • 18.6k
6 votes

Generational Loss of Data with DNA Testing

I am not an expert on DNA testing. But I learnt (and still learn) a lot through the story of Michael Lacopo at his blog "Hoosier Daddy?" where he blogs about how (tries) to find the biological father ...
  • 161
6 votes

Understanding chromosomes and centiMorgans

The closer your match generationally you will generally have more shared centimorgans (cMs). There is a published shared cM relationship range chart on the ISOGG website that gives a good general '...
  • 5,531
6 votes

Interpreting X DNA?

The oldest answer has given a great overview of X inheritance, and I agree with what it says. It does take study to understand. Initially I suggest you mainly rely on Coakley's two main charts of X ...
  • 3,857
6 votes
Accepted

Why are the lengths GEDmatch.com Chromosome Segment Matching segments not proportional to their cM?

The colored segments are not drawn in terms of cM, but in million base pairs (Mbp), which are the number shown on the bottom of your graphic. The numbers at the bottom are very approximate in position....
  • 16.5k
6 votes

Is a half-sibling match on AncestryDNA reliable, or is more testing needed?

Just a note that you should not automatically jump to the conclusion that you and your probably-half-sibling must share a father instead of a mother; young unmarried pregnant women were often ...
  • 1,860
6 votes

Does having child of DNA tested parent help find parent's DNA ancestors?

I will try to explain more comprehensively. What does phasing do and what task does it solve? We use phasing to separate the list of matches of one's person into two smaller lists of probable ...
  • 1,075
6 votes
Accepted

Does having child of DNA tested parent help find parent's DNA ancestors?

Edit: Brainstorm and I had an extended discussion through the comments on whether Visual Phasing of siblings can add information that the parent's DNA test doesn't already add. I have been convinced ...
  • 16.5k
6 votes
Accepted

Can my DNA results be wrong?

Unfortunately, the test can't be wrong. If it states that you have ONLY 1762 cM with this person, it means that you are in relations like uncle/niece or grandparents with their grandchild. Of course, ...

Only top scored, non community-wiki answers of a minimum length are eligible