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I’ll try to explain DNA testing as I understand it. First for genealogy there are primarily three types of testing. Y-DNA, MTDNA, X & Autosomal chromosome testing.


Now to explain the testing, you have to understand DNA. Each cell of the body has 23 pairs of chromosomes, in the cell but not in the nucleus  is mtdna. Notice here, the 23 pairs of chromosomes do  not include  mtdna.   When, the egg is fertilized the egg has 23 chromosomes and the sperm has 23 chromosomes. One pair of the chromosomes is used to indicate the sex of a child. The egg always carries a X chromosome and the rest are autosomal chromosomes. The sperm carries either the Y or the X chromosome and the rest are autosomal chromosomes.  Now if it is a boy child, you have a X and a Y for the pair of sex chromosomes.. Being there is only one “Y”… it cannot combine or recombine with every generation.  So the Y chromosome basically stays the same with few mutations (changes)  over generations. So a man’s parental (father/son) lineage can be proven by the results of the markers used in the Y-STR test.


I should add here that there are about  3 billion, 300 million Plus spots (markers/bases) that can be tested. There are different markers used for different tests. The markers used for Y-DNA testing normally are called Short Tandem  Repeats (STRs) and single-nucleotide polymorphism  (SNPs – pronounced Snips). SNPs normally are used for population migration. Where STRs are used for current genetic genealogy (basically - or in our case).  


single-nucleotide polymorphism:

short tandem repeat:


My Gilpin surname DNA project:


Y-chromosome DNA testing


FROM 23and  me

The Y chromosome is only present in males, and in one copy. Because the Y, unlike the X and autosomes, undergoes no *recombination* (or at least very little), it travels through the generations as a block, and therefore all of its SNPs record the same path through human history. This fact permits the ancestry of the Y to be resolved in much finer geographic detail than the recombining chromosomes. 


The first to understand is that to find a  DNA match the haplogroup of the pair of results being compared must match.. Example a man who has R1b haplogroup is not related  (with in the time frame of the use of surnames – 1000 – 2000 yrs)  to a man who has a Ib1 haplogroup.


Hapolgroups, depending on the testing company can be estimated by the first 12 STR markers of a Y-STR marker test. (normally test names are  just referred to by the number of markers tested as in 12 –25-36-44-67) To actually prove a haplogroup or to find a subclade of a haplogroup; a haplogroup test normally referred to as a deep clade test should be preformed. Also some companies test for particular haplogroup SNP markers. The markers tested for haplogroups are called SNPs.


Haplogroups, are the identifying terminology, for where you sit on the tree of humanity, it starts off with haplogroup Adam.. and after changes (mutations) in his SNPs a new haplogroup is created.. so over a few tens of thousands years, there developed  many different haplogroups. Some are descend and some are lateral  developments.  That is why a man who has R1b and a man who has I1b are thousands of years apart from a common ancestor.

Questions? Ask me.. (oh, Y haplogroups are named differently from mtdna haplogroups)


Now getting down to the very easiest, the Y-STR test used for genealogy. I said before that they are basically referred to (or called/named) by the numbers.  The 37 marker, YSTR test is the one I ask the members of my surname projects to use.  It has enough Fast mutating and slow mutating STR markers to make it a good identifying amount, the more markers the better but normally 37 is enough. What they do here is introduce a primer to the dna base at a particular place and count the reactions (spikes). The amount of reactions at a particular place (marker/base) is the result (there is an official name but it is still just a result)


To prove or disprove a relationship you compare the amount of the result to the result of the other person.  So example: man A -  marker DYS393=12; man B – DYS393=14  the steps of difference here is 2, all differences are accumulative.  At 37 markers, in my opinion; more then 4-5 steps of difference between two men make the common ancestor  before  the use of surnames.. Thus in the realm of current genealogy.. not related.



Y-DNA results:  




MTDNA Testing



the  ratio size of sperm to egg is exaggerated  here so you can see the MTDNA in both.


Next is MTDNA – mtdna is a chromosome but not part of the 23 pairs. It has a different job, it is primarily to produce and direct energy for the cell. Its mutations are very slow. A test of the MTDNA can have medical information. If you know what MTDNA SNP mutations indicate what medical information.


MTDNA is in both the cell of the egg and the sperm. But the mtdna of the sperm is primarily there to give energy to the sperm to swim to the egg and impregnate it.  Normally all the mtdna in the sperm is used up, when it isn’t the egg destroys the remainder. Thus you inherit the mtdna in your cells from only your mother. That is the reason it can be used to trace the maternal lineage. MTDNA, is different from the other chromosomes in that instead of being a string it is circular, and it is normally tested in HRV1 and HRV2 and the coding zone. I was told HRV1 and 2 start  basically if you were looking at a clock  - at 11:59 and end at 12:06 the rest is coding zone..and there are about 17,000 SNPs to test.


It is hard to use MTDNA for genealogy  because the maiden name changes with each generation where a man’s surname is passed  to each generation. I said hard, but it is not impossible, there have been many positive results.  You look for matching maiden names  and area locations.. Then you put the findings together. A matched maiden name, a matched time frame, a matched location, and matching mutations.


When testing MTDNA the results are very different from what you get with Y-DNA testing. There is a standard called Cambridge Reference Sequence, your results are compared to this and only the differences (mutations) are reported. So in this case you compare differences. To match, you and the person comparing must be the same differences from the CRS.


Mtdna –



X and autosomal testing



  Total 23 pairs


Now lets discuss the newest testing.. X and autosomal testing.

First, you inherit these 22 pairs of Autosomal chromosomes and the "X" chromosome from all your past ancestors (X chromosome inheritance pattern is a little different then the autosomals), second you might think you inherit 50% from each parent. NOPE…you inherit the  equal to 50%.  Since the X chromosome and the autosomal chromosomes  combine and recombine randomly, (x to x; auto to auto) the  further away from the common ancestor the lower the chance you have a measurable segment remaining from that ancestor. One problem that I see with this testing is that a negative result of a measurable segment from a common ancestor does not mean your not related, just that the part inherited is not measurable at this time.  

(You never know – this is cutting edge science.... five years ago.. this testing was not possible…the future holds surprises! ).

Now here is some additional information from some very knowledgeable people..




 From  - Dr. Ann  Turner in an email to me:

Females have two X chromosomes, one inherited from the father and the other
from the mother, so a connection in the X chromosome could be from either side of the family.
Males have one X chromosome, inherited from the mother. SMGF has a nice
animation showing the inheritance pathway:
Since not all ancestors can make a contribution to the X, you can eliminate
at least some of them as possibilities. See the diagrams on Blaine
Bettinger's site:

Note that the percentages are AVERAGES. A man's X chromosome can be exactly
the same as his maternal grandfather, exactly the same as his maternal
grandmother, or a mixture of the two, which works out to be average of 50%. I
find the demo Mendel family at 23andMe helpful in visualizing this. There are
three grandchildren and three grandparents, so you can look at different
combinations. (for 23 & me members) If they don't show up in your list of people you're sharing with, go to Account | Sharing | Example Profiles.


It will help you to phase the X (in other words, figure out who contributed what). This page helps tell how to do that:

If your genealogy program can print an ahnentafel chart, I've prepared a
file with the relevant ahnentafel numbers. Females should start the ahnentafel
with themselves; males should start with their mothers. Then you can go
through the ahnentafel report and delete the records of the people who could
not be the source of your X.  





The Chart



 If your a female then you put your name in the number one place. If your male then your mother goes in the number one position.

blue is male #2 is your father, pink-female #3 is your mother


See  the DNA Chart (shows how mtdna/Y-dna descends) - Link

My relatives charted for X chromosome genetics.








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Items below this line are not part of this website. provides the webspace,  owns and supports rootsweb, thus visiting the links once in a while helps support the use of free genealogy on