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Everything You Always Wanted To Know About DNA and Genetic Genealogy

                                                 But Never Asked

A Brief Overview of DNA

In 1953 James Watson and Francis Crick solved the mystery of identifying the molecular structure of the substance that was named deoxyribonucleic acid - DNA. Their descript of the "double helix" explained how the strands of DNA actually fit together and their model provided a means for microbiologists to further analyze and relate specific parts of DNA to biological phenomena and diseases. For this discovery, Watson and Crick were awarded the Noble Prize in Medicine and Physiology in 1962.

There are two types of DNA that are used in genetic genealogy and family history research:

1) DNA from the Y chromosome, which is found in the nucleus of all of our cells, is called Y-DNA. It is present only in males and transmitted in the male line from fathers to sons

2) DNA also occurs in the mitochondrion, outside of the cell nucleus, and is called mitochondrial or mtDNA. Males and females inherit and carry this mtDNA but it is only transmitted through females. A male will have his mother’s mtDNA but he will not transmit it to his children.  

Our Chromosomes. To understand how this DNA is used to create genetic profiles, we need to look first at how DNA is a part of our chromosomes. The DNA is the genetic material that occurs in the nucleus of all of the cells in our body. In our cells the DNA is composed of two strands, twisted around themselves, to form the double helix. For all humans, the DNA molecules are arranged into 46 chromosomes which occur in 23 pairs. In 22 of these pairs the material is identical with one being inherited from the mother and the other being inherited from the father. However, the 23rd pair, which determines gender, is composed of either two X chromosomes - which produces a female - our an X and a Y chromosome - which produces a male. This matching of X and Y chromosomes that occurs at conception is possible because, while the female's egg always contains the X chromosome, the male's sperm may contain either an X or a Y chromosome.

This explains why the male Y-DNA is used in genetic genealogy and why these patterns cannot be tracked using female DNA. The Y chromosome and DNA are inherited only by a male from his father and therefore it offers a unique record of paternal transmission. With the female's two X chromosomes there is a recombination or "exchange" of the DNA with that of the male's. This combining of DNA provides no opportunity for unaltered transmission of DNA material, as occurs with transmission of Y-DNA.
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Each male's unique Y-DNA are often referred to as "patterns," "signatures," or "fingerprints." The numbers ("alleles") that you see on the Project Chart next to each of our volunteers' names represent that individual's unique DNA profile based on 12 (or more) markers. Each profile will be identical to that of their brother's, son's, father's, grandfather's, great grandfather's.

Mutations. The only exception to the continuation of this unique string of DNA markers is when a mutation occurs. The Y chromosome is composed of 60 million identifiable pieces, called "letters," that record each individual's unique history and make-up. These letters actually represent the combinations of four chemicals in the double helix that make up all DNA (Adenine, Thymine, Cytosine, and Guanine). As each individual's DNA is copied and passed from one generation to the next certain "copying errors" or mistakes may occur. This is like a "typo." Many of these are repaired through chemical means quickly and most have no effect on the life of the individual within whom the mistake occurred. However, since the Y chromosome is the only one of the 23 pairs that does not exchange DNA, the errors that occur here will represent changes that are passed on to the next and subsequent generations.

These changes may represent the actual transposing of a letter, like an A for a T, or the insertion or deletion of letters or groups of letters. It has been estimated that a mistake or change in the basic DNA sequences may only take place once every 500 generations. If you look at our Project Chart you will see that the first DNA marker is called DYS 393. The numbers (alleles) for this marker from our volunteers range from 13 to 16. These represent the lengths or "repeats" that occur on this part of the chromosome. When you combine each of these markers, whether you use 12 or 25 markers, they will represent a unique pattern or profile.

Haplotypes. These profiles are also called haplotypes and represent simply each individuals unique pattern of DNA. These individual patterns may be compared to databases of other individual’s patterns and those with clear similarities can be combined into broader groups called haplogroups. In fact, these haplogroups can be identified with DNA patterns that existed in the earliest stages human development among unique ethnic and certain geographic human populations.

In our DNA Project we know have DNA profiles that represent two prominent haplogroups: R1b1 and I. We have 34 profiles that are representative of the R1b1 group and 23 profiles that represent the I group. Each haplogroup represents a clearly different family line in the overall picture of human evolution. Therefore it is said that individuals from differing haplogroups could not have a common ancestor for as many as 500 generations ago. Thus when we find Everett/Evered family lines living within close geographical proximity of one another in England, but representing clearly different DNA haplogroups we must assume that not only are they not related closely but that their descendants came from very different times and places.

The field of Anthrogenealogy combines knowledge of human groups and migrations (anthropology) with the science of DNA that can identify the earliest origins of humans.  The projected origins of our earliest Everett ancestors in these two haplogroups are as follows:

R1b1  This group is most common in Europe (Atlantic Modal Haplotype) and evolved from stone age hunters and gatherers who arrived in Europe about 40,000 years ago. They spread northwestward throughout Europe from northern Spain after the last glacial period ended 10-12,000 years ago.

 

I  This group dates back 23,000 years or longer but arrived in northwestern Europe only about 8,000 years ago. They are credited with introducing agriculture to southern and central Europe and their origins closely identified with early Anglo Saxon and Viking populations.

 

While these haplogroups represent the more prominent DNA profiles in our Project, we also have volunteers whose profiles represent three other haplogroups:

                        G (3 profiles), R1a (1 profile) and E3a (1 profile).

 

G  This lineage may have originated in India or Pakistan, and has dispersed into central Asia, Europe, and the Middle East.

 

R1a  This lineage is believed to have originated in the Eurasian Steppes north of the Black and Caspian Seas. It is thought to have descended from the Kurgan culture that is known for the domestication of the horse around 3000 bc. The group is most common in eastern Europe (Slavic), India, central and western Asia origins, and represented the first speakers of the Indo-European language group.

 

E3a  This is an African lineage that dispersed south from northern Africa within the last 3,000 years by the Bantu agricultural expansion. It is the most common lineage among African Americans and has recent origins in Senegal and Gambia.

Other significant haplogroups include the following:

Q3  Native American populations. Mutation occurred 8-12,000 years ago.

 

J2  Mediterranean, central Asia and India. It is common to Jewish populations

 

G2  This lineage may have originated in India or Pakistan, and has dispersed into central Asia, Europe, and the Middle East. The G2 branch of this lineage (containing the P15 mutation) is found most often in the Europe and the Middle East.

 

For more information on haplogroups review the Phylogenetic Tree at www.familytreedna.com/haplotree.html 

For more information on ancient human migrations see the National Geographic’s DNA research website on the Genographic Project at www3.nationalgeographic.com/genographic/atlas.html           

Most Recent Common Ancestors (MRCA). For the purposes of genetic genealogy, the closer that the numbers in the profiles match, the more recent is the likelihood that those "matching" individuals share a common ancestor. (Look at Robert's and Peter's 12/12 match in Cluster 1 and Vernon's and Craig's 11/12 match in Cluster 5.) Laboratories identify either 12, 25, 37 or 67 markers for genealogical research. Most surname studies, such as ours, begin with the 12-markers which can be refined to 25 or 37 from the original sample at a later time. The 12 markers are sufficient to differentiate basic family lines. Additional markers are helpful in determining the actual “closeness” between two individuals.

The interpretation of the differences of these markers is more complicated, but it is important to understand so that proper conclusions can be drawn. If there is a 12/12 match, as in Robert and Peter from England, then there is a 99% probability that they are directly related. Where there is an 11/12 match (as with Vernon and Craig in Cluster 5) or 10/12 match (as with Kenneth and Earnest Dale in Cluster 3) they will be "considered related," but the time frame in which their MRCA occurred may have been more distant than for those with a 12/12 match. Profiles with a 24/25 match or a 35/37 match will indicate a clearer MRCA. Profiles with less than a 10/12 match, for analysis purposes, are usually not considered to be closely related, at least within the time frame of recorded history.

The actual probability of defining MRCA relationships are as follows:

►A 12/12 match means that one's MRCA occurred between 1 and 62 generations ago. There is a 50% probability that the MRCA lived 14 generations ago (350 years ago), or less, and a 95% probability that the MRCA lived within 62 generations ago (1550 years ago). (Note: For the purposes of these predication, most scientists use 25 years to define a generation).

►An 11/12 match means that one's MRCA occurred between 1 and 122 generations ago. There is a 50% probability that the MRCA lived 37 generations ago (925 years ago), or less; and a 95% probability that the MRCA lived 122 generations ago (3050 years ago).

►A 10/12 match means that one's MRCA occurred between 1 and 166 generations ago. There is a 50% probability that the MRCA lived 61 generations ago (1525 years ago), or less; and a 95% probability that the MRCA lived 166 generations ago (4150 years ago).

These probability figures are supplied by the FamilyTreeDNA program, with which our Project works. Further information about genetics and a DNA tutorial are available on their website: http://www.familytreedna.com/facts.genes.asp.

 

Understanding the Role of Mitochondria (mtDNA)

Many female researchers have felt left out of this research process because of its reliance upon male DNA. As we mentioned above, this piece of DNA occurs outside of the nucleus of our cells and within a membrane in the surrounding cytoplasm. This DNA is found within structures called mitochondria (mt) and the DNA itself is identified as mtDNA. Technically, this mitochondria is used by cells to convert oxygen into energy. However, buried within each piece of mitochondria is a small piece of DNA. Unlike the DNA in the nuclei of our cells that we inherit from both of our parents (the X and Y chomosomes), this mtDNA comes only from our mothers. While both males and females carry mtDNA, it can only be passed on to offspring through the females.

The Y-DNA is used in our surname research projects, in part, because it does not blend (recombine) with the X-DNA, and also because it changes, or mutates, more quickly than the mtDNA.  It is estimated at one mutation occurs about every 500 to 750 years. The mutations, or changes in an individual's DNA are the key to reconstructing genetic history and identifying similar or differing family lines. If there were no mutations everyone’s DNA would appear essentially similar. It is the mutations, or patterns of mutations that occur in a specific family line that defines it and sets it apart. The mtDNA is unique in that it mutates more slowly and that while all humans carry the mtDNA it is only passed on by females. These changes that are recorded in the mtDNA's "molecular clock" allow the researcher to identify and track over enormous time periods broad patterns (Haplogroups) that have occurred over hundreds of thousands of years of human evolution.

This mtDNA has also become an important resource in medical research. Research has already identified certain mutations in the mtDNA that may control an individual’s susceptibility to diseases such as Parkinsons and Alzheimers, and a form of epilepsy. 

Brian Sykes, a professor of genetics at Oxford University in England, has become a well-known authority on DNA and its extraction from ancient sources. He and his team were the first in the world to recover traces of DNA in ancient human bones. In 1991 two hikers in the Italian Alps discovered the frozen remains of a male - later to be referred to as the "Iceman." Sykes successfully extracted mtDNA from the frozen bone fragments. The remains had been dated to between 5,000 and 5,350 years old by carbon dating methods. In his lab, Sykes compared the DNA profile of the "Iceman" with those in his database collected from a variety of living European samples. He found that the "Iceman" was definitely European. However, to his surprise, the "Iceman's" profile matched perfectly with a DNA profile collected from a lab worker (Marie) at Oxford. He observed: "This could only mean one thing. Marie was a relative of the Iceman himself. …there had to be an unbroken genetic link between Marie and the Iceman's mother, stretching back over five thousand years and faithfully recorded in the DNA (Sykes, 2001).

Sykes continued: "My research over the intervening decade has shown that almost everyone living in Europe can trace an unbroken genetic link (as Marie and the Iceman), way back into the remote past, to one of only seven women. These seven women are the direct maternal ancestors of virtually all 650 million modern Europeans. …I know that I am a descendant of Tara (one of the names given to the seven women, the "Seven daughters of Eve"), …I reckoned that Tara lived in northern Italy about 17,000 years ago. Europe was in the grip of the Ice Age, (but)….As the Ice Age loosened its grip, Tara's children moved round the coast into France. …Eventually Tara's children walked across the dry land that was to become the English Channel and moved right across to Ireland, from whose ancient Celtic kingdom the clan to Tara takes it name. (Sykes, 2001.)

Sykes’ projection of “Seven daughters of Eve” is somewhat controversial among geneticists, and most scientists now suggest that there are many more early family lines that can be traced with female origin.

Everett/Evered women researchers can follow the early origins of their female ancestors by ordering mtDNA tests. Since these cannot be used for genealogy research, we encourage them to enlist their male relatives to take the DNA test. Many of the family lines identified on our DNA Chart are being researched by women. Others have contributed to a “scholarship” fund whereby men interested in taking the DNA test but who cannot afford it have been offered financial help. You may contribute directly to a General Fund website at the following link: www.familytreedna.com/contribution.html .

These funds are held in the name of the Everett Surname Project and can only be dispersed, as needed, to order DNA kits for volunteers.

 

Reading resources in all areas of DNA and genetic genealogy can be found at the following link: http://www.familytreedna.com/pdf/GGAB.pdf . This link is an Annotated Bibliography developed by our Project’s administrator, Craig Everett.

 

For more information on the Everett DNA Project or if you wish to have a kit sent to you, contact Craig Everett at everett5@mindspring.com .