FAQ -  (Glossary of DNA Terms in Molecular Genealogy)

Molecular Genealogy - Y-DNA - DYS (Markers) - STR (Short Tandem Repeat) - Haplotype - Mutations - The Most Recent Common Ancestor (TMRCA) - Haplogroups - Matching Results, Relatedness and Common Ancestry - SNP - Deep Clade - Haplogroup Tables for R, R1, R1b, I and E

Molecular Genealogy ("Genetic Genealogy") is the application of DNA science to traditional genealogical research. Every genealogist has encountered the infamous "brick walls" in their genealogical research. These "brick walls" occur where there gaps or incomplete genealogical information. DNA if used correctly (and in conjunction) with traditional genealogical methodology can aid the tracing of ancestry and the making of connections with other families, when these "brick walls" occur. Molecular genealogy is based on probabilities; it is not an exact science. It can provide important clues for family history research, but traditional genealogy methods continue to be an important part of molecular genealogy.

Note: All information gathered here is better presented elsewhere, you can and should refer to these topics and subjects on www.smgf.org and www ftdna.com. IHDP promotes traditional genealogy and Irish Family History using Molecular Genealogy. IHDP promotes Molecular Genealogy as a tool of traditional genealogy. Here is IHDP's glossary of the terminology used in Molecular Genealogy.

DNA encodes the genetic blueprint of human beings. DNA is found in most cells in the human body, and is usually classified into three types that are useful in genealogy; Y-Chromosome DNA (Y-DNA), Mitochondrial DNA (mtDNA) and Autosomal DNA. IHDP is primarily concerned with Y-Chromosome DNA (Y-DNA).

Y-Chromosome DNA (Y-DNA):

This is a type of DNA that is only carried by men, inherited from fathers and passed down from father to son through the generations, along the male line. This male line is said to share a common paternal ancestor, as they all have similar Y-DNA.

Y-DNA is particularly useful for tracing one's direct paternal line (father, paternal grandfather, etc.) because it changes slowly from generation to generation. This is most useful, as the son in most societies usually inherits the surname of the father. Males who share a common paternal ancestor will have virtually the same Y-chromosome DNA.

DYS (Markers):

The Y-chromosome contains millions of bits of information, each of which is encoded by a "base pair." Analysis of all these base pairs is impractical for genealogical purposes.  Geneticists have identified a number of specific chromosome locations that can be used for analysis and comparison. These unique locations are generally called "markers" and when they occur on the Y-chromosome, they are typically given numeric values/names starting with the prefix "DYS", for example, DYS391.

STR (Short Tandem Repeat):

At some Y-chromosome locations (Markers), there are small segments of base pairs that are repeated in the DNA. Markers (DYS) with these types of repetitions are called "STR markers," where STR means "Short Tandem Repeat."

For example, a particular genetic sequence at the DYS marker location DYS391 might be: TGTCTG/TCTA/TCTA/TCTA/TCTA/TCTA/TCTA/TCTA/TCTA/TCTA/TCTA/TCTGCCT:

Note the ten repeats of the segment TCTA? The number of these repeats is the "value" that is shown on a YDNA test report for this marker (which is 10). Markers DYS385, DYS459, DYS464 and YCAII are often called "duplicate markers" since they have two (or more) values for each marker location. These locations are sometimes regarded as a single marker with two values, rather than two separate markers for example DYS385a and DYS385b.

STR’s repeat within certain ranges, each Allele has a different range. For example you might rarely see a 5 for DYS391, as it is known to repeat, on average, between 9 and 17 times. Though instances lower than 9 have been reported, as low as 7.

Haplotype:

This refers to a set of Y-chromosome STR marker values. A Y-DNA test report always shows a series of markers (DYS) and there corresponding values. These results are referred to collectively as a "haplotype."

For example; the following sequence; 13 24 16 10 15 15 11 13 12 13 11 30 would be called a 12-marker haplotype. See also Haplogroups

Important: Anthropologists break down the Y-chromosome into branches called Haplogroups or clades. Haplogroups are similar haplotypes grouped into a common classification. You can have a very close match 24/25, be the same Haplotype, but members of a different Haplogroup. Haplogroups are no indicator of relatedness. Haplogroups are useful for population and demographic studies, but be aware they do have a very limited application in traditional genealogy.

Note: In general, the more markers tested, the easier it is to distinguish individuals and family tree branches.

Mutations:

While DNA is slow changing, it does change, occasionally there are small changes or "copy errors" that can occur with each descendant. These copy errors are called "mutations" and are generally harmless, but are always useful for tracing one's direct paternal line.

For example, look at the following three same surname haplotypes (examples here have 25 Marker DYS values):

13 24 14 10 11 14 12 12 12 13 13 30 18 9 10 11 11 25 15 19 30 15 15 17 17
13 24 14 10 11 14 12 12 12 13 13 30 18 9 10 11 11 25 15 19 30 15 15 17 17
13 25 14 10 11 14 12 12 12 13 13 30 18 9 10 11 11 25 15 19 30 15 15 16 17

Note the first two “cousins” have exactly the same haplotype, but the third cousin has a difference of one marker value (16 instead of 17). This difference has been due to a mutation that occurred in his Y-DNA (or his father's), but not in the other two “cousins”.

Note: Generally the greater the number of mutations we find between two males, the further in the past their common paternal ancestor lived.

When comparing Y-DNA results you always look for the highest matching sequence. For example, if we look at the following two Y-DNA haplotypes (two sets of marker results):

13 25 14 10 11 14 12 12 12 13 13 30 18 9 10 11 11 25 15 19 30 15 15 17 17
13 25 14 10 11 14 12 12 12 13 13 30 18 9 10 11 11 25 15 19 30 15 15 16 17

Notice all the values are identical except for one. The conclusion would be the two participants might be related. The examples shown here are for 25 Marker Haplotype matches. In this instance it would be a good idea to further test additional markers (37+) to check for relatedness.

Matches on a 25 marker gives 95% probability of having a common ancestor within the last 600 years
Matches on a 37 marker gives 95% probability of having a common ancestor within the last 300 years
Matches on a 25 marker gives 95% probability of having a common ancestor within the last 200 years

Source: www.ftdna.com

Note: Generally the higher the percentage of matching markers, the closer two participants are related.

Matching Results, Relatedness and Common Ancestry:

When sharing a common surname, the higher matches of 33/37, 34/37, 35/37, and 36/37, indicates a common ancestor in the time that public records may have been in existence. Public records begin at various times in different locations, it might be more accurate to say within the existences of surnames. Family trees and paper trails can still date back that far. Individuals with matches of 33/37+ and higher may have intersecting ancestries.

Matches of 32/37 and higher; but to a different surname, may indicate a surname change in one line or may be coincidence. A coincidence can be environmental or more likely because that haplotype is more common.

Important: In Irish genealogy the matches between different surnames is complicated by the close genetic relationship between different surnames and Irish Kinship. O'Farrel branched off from MacRannell in the late 13th Century. Other examples, MacMahon from O'Brien, even in the later Middle Ages, the Clandeboye O'Neills who already branched off the O’Neill, then in turn broke into three separate dynasties. There are five dynastic branches of the MacCarthy's, seven of the main O'Neill dynasty. Even the great Norman Lordships fractured into different dynastic branches, with about five branches of the Burkes. But in general these branches and this dynastic fracturing took place BEFORE records begin, this important point should be borne in mind.

With Matches of 32/37 or less, generally these indicate a more distant connection, before the widespread use of public records. Matches of 33/37 can also be ambiguous and should generally be interpreted in the context of family history.

SNP:

There is another type of DNA mutation which is called a Single Nucleotide Polymorphism (SNP). A SNP is a change in a single base pair on the DNA molecule. SNPs on the Y-chromosome are very rare, but when they occur, they are passed down unchanged from father to son for literally hundreds of generations. SNPs are used to define entire populations of men. Populations that have the same Y-SNPs are said to belong to the same haplogroup. 

TMRCA:

The Most Recent Common Ancestor is the closest direct paternal ancestor that two males have in common (such as a grandfather or g-g-g-grandfather). Generally, the closer the match between two individuals the shorter the time back to their most recent common ancestor.

Some examples: if two individuals share 35 out of 37 markers, they almost certainly share a more recent common ancestor than two individuals who share 32 out of 37 markers.

Note: The time to a Most Recent Common Ancestor is based on probability and is not an exact science. TMRCA is better defined as a period of time rather than a specific time.

TMRCA is useful in one other aspect; finding ancestry locations in Ireland. In Ireland before 1650, most surnames would have been static for centuries, in their locales.

How to use your exact matches Last Known Ancestors to find your surnames location in Ireland:

1. Examine and note your higher exact matches (25/25, 33/37 up to 37/37) to different surnames
2. Check the exact matches stated Last Known Ancestors geographic location in Ireland.
3. You can also check where these surnames (and your own) were located in the 17th century in Ireland.

By doing this it may be possible to pinpoint a specific area or region for further research. Even in more recent times, if all your exact matches are to Irish people and all in a specific location, it is there you should target for your family genealogical research. This is one example of how you can "Leap-frog" the "Brick-walls"

Haplogroups, Clades and SNP's:

Anthropologists classify the Y-chromosome into branches called Haplogroups or clades. Letters, such as, Haplogroup J or Haplogroup Q, classify Y-chromosome haplogroups. Most haplogroups are subdivided into smaller groups. For example, Haplogroup R is divided into "R1a" and "R1b" and R1b is further divided into R1b1, then, a, b, c etc

Deep Clade tests:

Deep Clade tests are carried out on SNPs, to determine which haplogroup, or major branch of the Y-chromosome tree, a male test result belongs to. Once your Haplogroup is known, you can then use a Deep Clade Panel to test and identify the SNP mutations that occurred to help find your branch on the Y-chromosome tree.

SNPs will have been verified to see the frequency they occur in the male population to identify a branch on the Y DNA tree. The process of verifying and classifying the SNP, involves testing a statistically relevant population sample of males and determining a corresponding time frame which identifies the SNP as having value.

Important and Remember! Haplogroups are useful for population and demographic studies, they have a very limited application in traditional genealogy. Always remember Molecular genealogy is based on probabilities, it is not an exact science. As more people test Haplogroup classifications are liable to change.

Common Haplogroups and SNP values R1b, R, E, I

Have you have ever wondered what exactly R1b1c3 means? SNP testing results are displayed so that you can see what you are (+) and which SNPs you can rule out (-) (at this time – these can and will change).

R1b Haplogroup R1b SNP variations
SNP Values	R	1	b	1	a, b, c	1 to 8
R=	M207+
R1=	M207+	M173+
R1b=	M207+	M173+	M343+
R1b1=	M207+	M173+	M343+	P25+
R1b1a=	M207+	M173+	M343+	P25+	M18
R1b1b=	M207+	M173+	M343+	P25+	M73
R1b1c=	M207+	M173+	M343+	P25+	M269+
R1b1c1=	M207+	M173+	M343+	P25+	M269+	M37
R1b1c2=	M207+	M173+	M343+	P25+	M269+	M65
R1b1c3=	M207+	M173+	M343+	P25+	M269+	M126
R1b1c4=	M207+	M173+	M343+	P25+	M269+	M153
R1b1c5=	M207+	M173+	M343+	P25+	M269+	M160
R1b1c6=	M207+	M173+	M343+	P25+	M269+	SRY2627
R1b1c7=	M207+	M173+	M343+	P25+	M269+	M222
R1b1c8=	M207+	M173+	M343+	P25+	M269+	P66
Examples in Green above, differences below in red: R1b1c3 = M207+M173+M343+P25+M269+M126 R1b1c7 = M207+M173+M343+P25+M269+M222

  

R Haplogroup SNP variations
SNP Values	R	1	a	1	variants	2
R	M207+
R1	M207+	M173
R1a	M207+	M173+	SRY10831.2
R1a1	M207+	M173+	SRY10831.2	M180
R1a1a	M207+	M173+	SRY10831.2	M180	M56
R1a1b	M207+	M173+	SRY10831.2	M180	M157
R1a1c	M207+	M173+	SRY10831.2	M180	M87
R2	M207+					M124
Examples in Red above, differences below in red: R1a1a = M207+M173+SRY10831.2M180+M56 R1a1b = M207+M173+SRY10831.2M180+M157 R2 = M207+M124

  

E Haplogroup SNP’s
SNP Values	E	3	b	# 1,2,3,4	a,b	1
E	M96+
E3	M96+	P2+
E3b	M96+	P2+	M35+
E3b1	M96+	P2+	M35+	M78+
E3b1a	M96+	P2+	M35+	M78+	M148
E3b2	M96+	P2+	M35+	M81+	M81
E3b2a	M96+	P2+	M35+	M81+	M107
E3b2b	M96+	P2+	M35+	M81+	M165
E3b3	M96+	P2+	M35+	M123+
E3b3a	M96+	P2+	M35+	M123+	M34
E3b3a1	M96+	P2+	M35+	M123+	M34+	M136
E3b4	M96+	P2+	M35+	M281
	E	3	a
E3a	M96	P2	M2
Examples in Blue above, differences below in red: E3b3 = M96+P2+M35+M123+  E3b3a = M96+P2+M35+M123+M34

 

I Haplogroup I SNP variations
	I	1	a,b,c	2,3,4
I	M170+M258+P19	P38+
I1	M170+M258+P19	P38+
I1a	M170+M258+P19	P38+	M253+M307+P30
I1a2	M170+M258+P19	P38+	M253+M307+P30	M21
I1a3	M170+M258+P19	P38+	M253+M307+P30	M72
I1a4	M170+M258+P19	P38+	M253+M307+P30	M227
I1b	M170+M258+P19	P38+	P37.2
I1b2	M170+M258+P19	P38+	P37.2	M26
I1b2a	M170+M258+P19	P38+	P37.2	M161
I1c	M170+M258+P19	P38+	M223
Examples in Green above, differences below in red: I1b = M170+M258+P19+P38+37.2 I1b2a = M170+M258+P19=P38+P37.2+M161