DNA

YDNA Tests
Human sex is determined by the X and Y chromosomes. A female has 2 X-Chromosomes and a male has an X and a Y-Chromosome.
When a child is conceived it gets one chromosome from its mother and one chromosome from its father. The chromosome from the
mother will always be an X, but the chromosome from the father may be either X or Y. If the child gets the X she will be a girl, if the child
gets the Y he will be a boy.
This Y-Chromosome has certain unique features:
The presence of a Y-Chromosome causes maleness. It is transmitted from fathers only to their sons.
Most of the Y-Chromosome is inherited as an integral unit passed without alteration from father to sons, and to their sons, and so on,
unaffected by exchange or any other influence of the X-Chromosome that came from the mother. It is the only nuclear chromosome that
escapes the continual reshuffling of parental genes during the process of sex cell production.
It is these unique features that make the Y-Chromosome useful to genealogists.
An individual's test results have little meaning on their own. You cannot take these numbers, plug them into some formula and find out
who your ancestors are. The value of the test results depends on how your results compare to other test results. And even when you
match someone else, it will only indicate that you and the person you match share a common ancestor.

In testing YDNA, you will select how many markers to have tested. The number of markers is a method of selecting how detailed you want
the test to be. The higher the number of markers, the more resolution you will have in comparing the results with another person. Here
are the times back to the MRCA (Most Recent Common Ancestor) when ALL the markers match. Those numbers are based in the latest
results of the mutation rate study conducted by the University of Arizona. For example, with 37/37 (all 37 markers match), there is a 50%
probability that the MRCA was no longer than 2 generations, and a 90% probability that the MRCA was within the last 5 generations. With
25 markers, there is a 50% probability that the MRCA was within the last 3 generations, and a 90% probability that the MRCA was within
the last 10 generations., while with 12 markers, there is a 50% probability that the MRCA was within the last 7 generations, and a 90%
probability that the MRCA was within the last 23 generations.

tDNA Tests

Mitochondrial DNA (mtDNA) is contained in the cytoplasm of the cell, rather than the nucleus. This type of DNA is passed by a mother to
both male and female offspring without any mixing, so your mtDNA is the same as your mother's mtDNA, which is the same as her
mother's mtDNA. While YDNA traces a paternal line and is usually associated with a surname, mtDNA traces your maternal line, mother to
grandmother to great-grandmother and so on back following a maternal line and is not associated with a surname. It is important to keep
in mind with this test that a male's mtDNA comes only from his mother and a male does not pass it on to his offspring.

mtDNA changes very slowly so it cannot determine close relationships as well as it can determine general relatedness. If two people have
an exact match in their mtDNA, then there is a very good chance they share a common maternal ancestor, but it is hard to determine if
this is a recent ancestor or one who lived hundreds of years ago.
An exact match on the first hypervariable region, HVR1, is sometimes called a low resolution match. When they also share the same
haplogroup it indicates a possible connection. An HVR1 match has a 50% chance of a common ancestor within fifty-two generations.
That is about 1,300 years.
An exact match on both the first and second hypervariable regions, HVR1 and HVR2, is sometimes called a high resolution match. When
they also share the same haplogroup it indicates a possible connection. A match on HVR1 and HVR2 has a 50% chance of a common
ancestor within twenty-eight generations. That is about 700 years.

Haplogroups
Haplogroups are DNA test results which correspond to an ethno-geographic group. Thus it can be considered as the DNA equivalent of
a "tribe". The haplogroup is generally associated with the migratory path of ancient peoples.
A Y-DNA or mtDNA test will usually result in a haplogroup prediction.
The haplogroup correlates your test results to the closest geographic group sharing the same genetic markers and indicates the most
likely ethnic group and migratory path of your ancestors.