The Tyner/Tiner DNA Project
DNA Molecule

Tyner/Tiner DNA Project

What It All Means

Who/what/where?

For genealogical purposes Y-DNA and MtDNA tests are taken. Y-DNA passes from father to son. Biological brothers will have the same DNA, which was passed from their father. Their Uncle would have the same DNA as their father, which would be the same as theirs. MtDNA passes from mother to daughter and son. The son does not pass his mother's DNA to his children. His children would carry their mother's MtDNA. The daughter passes her DNA to her children. The MtDNA test would be used to go from your mother to her mother, etc.

Depending on the company the test would be taken by either a cotton swab or a small scrapper, used to rub the inside of your cheek. Test results return in 2 to 4 weeks. Your results may be emailed to you or you might have to search their database. You might receive email notifications when another results matches yours. Click here for more information about testing.

The Y Chromosome:

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: 

It is these unique features that make the Y-Chromosome useful to genealogists.

What does it mean?

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. Depending on the number of markers tested and the number of matches it will indicate with a certain degree of probability how long ago this common ancestor existed. It will not show exactly who this ancestor is.

 

Based on the above assumptions we derive the cumulative probability table below. This table simply list the number of generations corresponding to the 50%, 90% and 95% probability levels for various numbers of matches.

Match

50%

90%

95%

95% Confidence Interval

12-0

Match exactly at all 12 markers 

14

48

62

1-77

11-1

11 exact matches, 1 mismatch 

37

85

103

5-121

10-2

10 exact matches, 2 mismatch 

61

122

144

14-165

25-0

Match exactly at all 25 markers 

7

23

30

0-37

24-1

24 exact matches, 1 mismatch 

17

40

48

2-57

23-2

23 exact matches, 2 mismatch 

28

56

66

6-75
The TMRCA for 12 markers assumes that there are ONLY 12 markers available for testing. If there are only 12 markers and you match 12 for 12, there is a 50% probability that you share a common ancestor within 14 generations

The TMRCA for 25 markers assumes that there are ONLY 25 markers available for testing. If there are only 25 markers and you match 25 for 25, there is a 50% probability that you share a common ancestor within 7 generations

This table tells us that if we match on 24 of 25 markers there is a 50% probability that the most recent common ancestor is 17 generations or less, a 90% probability that TMRCA is 40 generations or less, and a 95% probability that TMRCA is 48 generations or less. The 95% Confidence Interval is the upper and lower range of values that encompass 95% of the probability for the TMRCA . If we match on 24 of 25 markers, 95% of the possible TMRCA values fall between 2 and 57 generations.

No!  A mutation is just a change in DNA.  Mutations are not necessarily harmful; in fact, most mutations don't do anything at all.  Occasionally a mutation may cause a disease (like hemophilia), or a condition (like deafness or dwarfism), or a harmless physical variation (like green eyes).  Sometimes a mutation may even be helpful.  For example, Europeans have a simple genetic mutation that reduces the amount of dark pigment in the upper layers of the skin.  This mutation helps children growing up in foggy, northern climates avoid vitamin D deficiency (rickets).  People with fair skin have an advantage in places like Ireland and Scandinavia, although they are prone to sun burn and skin cancer if they move closer to the equator.  Fair skin is an example of a mutation that is helpful in some environments and harmful in others.

Mutations

As discussed above, the Y-Chromosome is passed from father to son. The vast majority of the time the father passes an exact copy of his Y-Chromosome to his son. This means that the markers of the son are identical to those of his father. However on rare occasion there is a mutation or change in one of the markers. The change is either an insertion or a deletion . An insertion is when an additional repeat is added to a marker. A deletion is when one of the repeats is deleted. 

Mutations occur at random. This means it is possible for two distant cousins to match exactly on all markers while two brothers might not match exactly. Because of the random nature of mutations we must use statistics and probability to estimate the T ime to the M ost R ecent C ommon A ncestor ( TMRCA ). The actual calculations of TMRCA are mathematically complex and depend on knowing the rate of mutation and the true number of mutations. At this time there is not enough data to accurately determine either of these factors so certain assumptions have to be made. The discussion of these assumptions and the actual calculations are beyond the scope of this webpage. For those wishing to read more about the various models used, I recommend Time to Most Recent Common Ancestry Calculator by Bruce Walsh. The simplest and one of the most commonly used models makes the following assumptions: