DNA made simple!

1. The Y-Chromosome test traces the MALE line only. If M0 took this test then it would trace through the left-outermost branch of the chart below.

M0-M1-M2-M4-M8

If a match was found with another male who had been tested then that male is descended from the same male lineage. You cannot tell exactly WHERE the linkage is between the two male researchers, only that they have a common male ancestor SOMEWHERE on their trees on the left-outermost branch continuing back in time.
If a researcher wanted to connect a surname with the surname of M7 one would need to obtain a sample of M7's male descendents i.e. a brother of F3.

Of course if M0 is not interested in genealogy but his sister F0 was, then she could arrange for M0 to take the test (of course she would have to pay!). In this way we can use the Y-Chromosome tests for many of our family lines if we can find living male relatives on the lines we want to test.
Table 1. Using the Y Chromosome employing your brothers, sisters and cousins!

M - Male       F - Female

M8

+

F8

M9

+

F9

MA

+

FA

MB

+

FB

MC

+

FC

MD

+

FD

ME

+

FE

MF

+

FF

I

I

I

I

I

I

I

I

M4

….

+

….

F4

M5

….

+

….

F5

M6

….

+

….

F6

M7

….

+

….

F7

I

I

I

I

M2

….

….

….

+

….

….

….

F2

M3

….

….

….

+

….

….

….

F3

GrandFather

I

I

GrandMother

I

I

M1

….

….

….

….

….

….

….

+

….

….

….

….

….

….

….

F1

Father

I

Mother

I

I

I

I

Brother

M0

F0

Sister

2. The mtDNA test on the other hand is tracking DNA that is passed only through the Mother's line and cannot be passed on through the male line.

In this case M0 or his sister F0 can be tested (it makes no difference). However the line tracked now is on the right-outermost branch of the chart.

F0-F1-F3-F7-FF
M0-F1-F3-F7-FF

If a match is found in this case between two researchers, then they ARE related, they share a common female ancestor, somewhere.....

For any family branches 'inside' the chart, i.e. not the outermost-male or outermost-female branches then you have to find cousins, uncles, aunts etc. on those lines who would make a Y-chromosome or MtDNA test worthwhile for those branches (i.e. on THEIR chart you are now looking at the outermost branches).

In general it is better for older generations to be tested rather than younger. This is true for several reasons, including:

1. There is less chance of false paternity creating surprises in the data, and
   
2. If the older relative is the last surviving male in that line then it is a good idea to have them tested while you have the chance..... This is the same as failing to interview a last remaining Uncle while they can still give you vital data.
   

Taken from FamilyTreeDNA 


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