Most cells in our body have two types of DNA, chromosomonal and mitochondrial. We all have 46 chromosomes located in the nucleus which constitiutes the chromosomal DNA. There are also structures outside the nucleus, termed mitochondria, that have their own small genome (approximately 16,500 base pairs long). Ancestry genetic tests take advantage of these two types of cellular DNA. There are three basic types of ancestry genetic tests:
These genetic tests analyze different DNA molecules, sequence different regions of DNA withiin those molecules, and compare results to various DNA sequence databases. The actual methods utilized, and DNA databases analyzed, by the nearly 30 companies currently offering ancestry genetic testing are different. Genomic Express has selected Ancestry.com as a preferred provider of ancestry genetic tests. Ancestry.com has the largest collection of historical records and searchable databases for ancestry/genealogy research. We provide information and educational resources regarding ancestry genetic testing here on our website. When you decide which test is most appropriate for you, you will be directed to DNA.Ancestry.com who will send you your DNA testing kit, perform the genetic test and provide youjr ancestry report.
Determination of DNA sequences in certain regions, termed markers, of the Y chromsome yields information about paternal ancestry. Women wishing to learn more about their paternal lineage may ask a male relative, such as their brother or father, to undergo Y DNA testing. This ancestry genetic testing can give you information about your paternal lineage dating back many thousands of years. It can also tell you about the geographic origin of your roots. Furthermore, this genetic testing can tell you the likelihood that you may be related to other people who have undergone the same ancestry genetic test. Most Y DNA tests analyze between 12 and 67 different markers. It has been estimated that if two individuals have 37 of the same markers, then they have a 50% probablility of sharing a common ancestor in the last 5 generations and a 90% probability of sharing a common ancestor within the last 17 generations. This is referred to as a most recent common ancestor (MCRA). If two individuals match on fewer Y DNA markers, their MRCA is further distant whereas if they match on more markers their MRCA would be more recent.
Most of the markers in Y DNA testing are short tandem repeats (STRs) which are short DNA sequences (such as TCA, GATA, etc.) that are repeated at certain postions (loci) on the chromosome. In different individuals, the numbers of repeats may vary, for example, from 7 to 30 copies. When individuals have the same number of repeats at a locus, it inidcates a degree of relatedness. The more loci at which individuals have the same number of repeats, the more closely related they are.
In addition to estimating the time of the MRCA, paternal lineage tests can tell you from which ancient lineage you are descended. Human life is estimated to have originated in Africa between 175,000 and 200,000 years ago. As humans migrated out of Africa, there arose geographically isolated groups. Through the process of mutation, selection and in-breeding, these groups acquired different characteristics such as eye and hair color, skin tone, stature, etc. The major geographic regions of the world for ancestry determination are considered to be Africa, Europe, Eastern Asia and the Americas. Y chromosome analysis will reveal your ancient paternal lineage. These are referred to as haplogroups, and there are 18 major paternal haplogroups (termed A through R). Paternal haplogroups can be further subdivided into subclades.
Since mitochondria are present in eggs but not sperm, they are exclusively inherited from mothers. Analyis of mtDNA, therefore, yields information about your ancestry on your mother's side of the family. Certain regions of mtDNA are sequenced and compared to databases containing mtDNA sequences generated from many people of different ethnicities and from different geographic regions of the world. This genetic testing can give you information about your maternal lineage dating back thousands of years. It can also tell you about the geographic origin of your roots on your mother's side. For example, if you are of European descent, mtDNA testing can trace your maternal lineage to one of the "Seven Daughters of Eve" 2 . These are pre-historic women who gave rise to different European lineages and shared a common ancestor, who has been called "Mitochondrial Eve".
Autosomal DNA refers to the 22 pairs of chromosomes other than the X and Y chromosomes. Due to genomic DNA sequencing advances, the databases for ancestry related autosomal DNA sequence variations has significantly improved in recent years. Analysis of autosomal DNA sequences can now provide more detailed ancestry related information than X and Y chromosome analysis alone.
Genomic Express has selected Ancestry.com as a preferred provider of ancestry genetic tests. Ancestry.com has the internet's largest collection of historical records and searchable databases for ancestry/genealogy research. Ancestry.com currently offers autosomal DNA analysis testing of over 700,000 SNPs. If you wish to purchase an ancestry genetic test, the "Order Now" links on this page will direct you to DNA.Ancestry.com who will send you your DNA testing kit, perform the genetic test and provide your ancestry report.
1 Wells, S. (2006). Deep Ancestry: Inside the Genograsphic Project: the Landmark DNA Quest to Decipher Our Distant Past. (National Geographic Society, publisher).
2 Sykes, B. (2001). The Seven Daughters of Eve. (W.W. Norton and Company, publisher)