DNA Analysis for Genealogy

When reproduction occurs, chromosomes from the mother and the father combine to form the chromosomes for the offspring. The DNA in these new chromosomes provide the genetic information for the individual, the so-called genome. To date, DNA that has been mixed in this way has not been of use to genealogy, as there is no way to relate the offspring’s DNA with those of the parents. There are two (and only two) sources of DNA, however, that do not mix the mother’s and the father’s DNA. Consequently the DNA from these sources provide information that is genealogically useful. Fortunately, one comes from the father and the other from the mother. The Lambert DNA Project is based on one of these sources.

Each son receives DNA for his Y chromosome from his father. This DNA is not mixed with that of the mother, and it is identical to that of the father, unless a mutation occurs. It has been estimated that a mutation occurs about once every 500 generations, or every 15,000 years, give or take a few millennia. Because we look at several different sites on the Y chromosome, however, we do have to worry about mutations. The more sites examined, the more likely mutations are present.

Y chromosomal DNA (Y DNA for short) is passed on from father to son. It represents a nearly unbroken chain that moves through all recorded history and into the cloudy prehistory of our Neolithic and Paleolithic ancestors. The qualifier “nearly” is inserted to remind us that mutations are possible. Starting with the living donor of Y DNA, the genetic information is inherited from the donor’s father, from that man’s father, and so on, up the male, or paternal, or Adam line. It provides a fingerprint of this particular line. Barring mutations, two brothers would carry this same Y DNA, as would two first cousins who were the sons of brothers, or a nephew and his paternal uncle. In most Western cultures, these men would all have the same surname. The Y DNA thus becomes a genetic label for the surname. Comparison with other men with the same surname could confirm whether they had a common ancestor.

Y DNA within such a family group may not match, because of what are delicately called “non-paternal events.” There are three causes for such events. An adopted individual would carry the surname of his new family but the Y DNA of his birth father. An individual who chooses to change his name would bequeath his new surname to a son along with the Y DNA of his father, who carried the original surname. Finally, as the result of illegitimacy a son will carry the surname of the cuckolded husband of his mother (or the surname of his unmarried mother) but his DNA is that of his genetic father. Often the first two causes can be anticipated through research of historical or family records. Genealogists have had to assume that no illegitimacy occurred.

The Lambert DNA project uses FamilyTreeDNA for analysis of the samples. The results of the analysis are the identification of numerical categories for 12, 25, 37, or 67 pieces of Y DNA, depending on which test the participant chooses. These pieces were chosen because they are among the fastest mutating parts of the DNA. The faster the mutations, the more opportunity the genealogist has to distinguish different families or subgroups of families. The pieces are referred to by a DYS label (for “DNA Y Segment”). Within each segment (also called a locus or a marker), certain molecular components are repeated, so that the segments have been called “short tandem repeat” (STR) units. The components may be repeated say 10 or 15 or 27 times. These repetition numbers are what we get from the DNA analysis. Mutations have resulted in variations of the repeat number for a given marker within the population. A particular STR such as #390 might occur in different individuals as different variants or alleles, possessing say 22 or 23 or 24 repeats. The smallest commercial analysis uses 12 markers. The list of results for a 12 marker analysis looks something like this.

This particular set of results, called a haplotype, is for the Lambert who is the administrator of the Lambert DNA Project. It is usually considered that three unit deviations from these 12 numbers indicate little relationship between two individuals. Even when two individuals have identical numbers for all 12 markers, they still may not be closely related. For further information, more markers are needed, for which FamilyTreeDNA provides the 25 marker test, which includes the additional markers with DYS labels 458, 459a, 459b, 455, 454, 447, 437, 448, 449, 464a, 464b, 464c, and 474d. For even higher resolution, 37 or 67 marker tests are available. Because of the greater amount of information in the 25 marker test, we recommend it even for an initial test. The 12 marker test, however, is less expensive and suffices in some cases.

The pattern of alleles allows the individual to be placed into genetic categories, or haplogroups, that have been established for large populations. These groups were established by analysis of individuals still living in their ancestral homeland, preferably going back thousands of years. Because any number of migrations could have taken place over the thousands of years since a given haplogroup was established, it is difficult to assign specific ancestral locations. Thus the haplogroup I1a, possessed by many Lamberts, is associated with Scandianavian and Anglo-Saxon populations. It is thought to have come from the Gravettian culture that arrived in Europe about 25,000 years ago from Southwest Asia. The culture was known for Venus figurines, shell jewelry, and houses constructed of mammoth bones. The most common haplogroup in western Europe, R1b, also is the most common found among Lamberts. It is associated with the men who repopulated Europe after the most recent ice age 10,000 years ago.

The results of Y DNA testing on the one hand can provide identification of the haplogroup, with interesting information about the deep history of your paternal line. On the other hand, comparisons of one person’s haplotype with that of others with the same surname (or even with different surnames) can lead to conclusions about the relationships among these individuals. Drastically different haplotypes imply little or no relationship. Identical or nearly identical haplotypes, particularly at the 25 marker level, allow statements to be made about how recently their common ancestor lived.