Genealogical DNA Tests and Links Kathy Sztanko 17th November 2017 Genealogical DNA Testing A genealogical DNA test is a DNA-based test which looks at specific locations of a person's genome in order to determine both their ancestral ethnic groups and genealogical relationships by comparison with other results. These different types of results are possible because different markers within the DNA change at different rates - ethnic markers change extremely rarely, family markers more frequently. Uses of Genealogical DNA Testing A genealogical DNA test may: ● help to verify your family tree ● provide helpful clues to inform the future direction of your research ● possibly help to break down long-standing brick walls It can’t provide you with an instant family tree It’s value lies in the comparison process, so it’s important to test with a company that has a matching database and to have a good tree based on genealogical records to start with. What is a genome? A genome is all of a living thing's genetic material, it contains around 20,000 genes (single molecules of DNA), packaged in 23 chromosomes which affect the characteristics of the organism Human DNA is 99.9% the same between individuals, DNA tests look at the 0.1% that is different Unless you are an identical twin, your genome is different from that of every other person on earth, in fact, it is different from that of every other person who has ever lived Where does your genome come from? Humans have 22 pairs of autosomal Chromosomes (which are the same in males and females), plus one pair of sex chromosomes that differ, being XX in a female and XY in a male. During reproduction each cell copies itself then divides twice so each new cell contains half the normal number of chromosomes which combine with those from the other parent to produce a mixture of characteristics. What is DNA? A DNA molecule is a double helix, a structure that looks like a ladder twisted into a spiral. Each rung of the ladder is made of two bases linked together in the middle. Bases are coded with the letters A,C,G & T. The length of a DNA molecule is often measured in "base pairs”. When DNA replicates the ladder disconnects and makes a new partner, sometimes mistakes are made during this process and sections are duplicated or lost. These are the markers that are tested. DNA Stability and Haplotypes Genealogical DNA testing looks at the portions of the DNA that have no known function. Generally these stretches of DNA remain unchanged from generation to generation. But chance changes (called mutations) do infrequently occur and it is these changes that distinguish different lines of descent and determine how closely people may be related to each other. It is estimated that the human Y-chromosome accumulates roughly 2 mutations per generation. Mitochondrial DNA mutations occur less frequently. Haplogroups and Ethnicity A DNA sequence that is passed on unchanged from one parent to a child is called a haplotype, these are the distinctive patterns used to establish genealogical links. Haplotypes can be grouped into Haplogroups (broad population groupings which diverged thousands of years ago). Each haplogroup (or clade) is a group of similar haplotypes that share a common ancestor. People with different haplogroups cannot be related. Clades often have origins in particular geographical regions and are used to indicate ethnic origins. Common ancestors Male & female haplogroups are different and do not relate to one another in any way. We all ultimately share a common male ancestor known as “Y chromosome Adam” and a common female ancestor known as “Mitochondrial Eve”. These ancestors did not live at the same time and were not the only males and females around at the time. But they are the only male and female whose DNA has come down to the current day. Types of DNA test 1 The first commercially available DNA tests for family historians became available in 2000 but were very expensive, since then testing companies have proliferated and prices dropped. Y-DNA – traces paternal ancestry up the male line and is used for surname projects. It can only be taken by males. Mitochondrial (Mt)DNA – traces maternal ancestry up female line. Mitochondrial DNA is carried by males and females but only passed on by females. Types of DNA test 2 Y-DNA & mtDNA cannot be used for ethnicity estimates, but can be used to indicate one's haplogroup. Autosomal (at)DNA – traces both male and female lines and indicates potential cousins. Also known as Family Finder or Cousin Matching. Types of DNA test 3 Which type of DNA test/company The choice of test will depend on the questions that you want to answer. A DNA test can be considered as an investment and the value of the test will grow as more people join the databases and you get more matches. The two main companies are: FTDNA – all three tests Ancestry – autosomal only FTDNA FTDNA is the market leader for both Y-DNA & mtDNA testing with over 600,000 Y-DNA records & over 250,000 mtDNA records. It has the world’s largest Y-DNA & mtDNA genealogical matching databases. They are the only company that allows complete integration of Y-DNA, mtDNA and autosomal DNA test results for genealogical purposes. They host a wide variety of surname projects, haplogroup projects (Y-DNA and mtDNA) and geographical projects, currently 9,778 altogether. Experienced and knowledgeable volunteer project administrators can often provide advice and help with the interpretation of results. Matches are more likely to be responsive and interested in genealogy. The size of the Family Finder database has not been disclosed but is likely to be 500,000+. Ancestry AncestryDNA has been responsible for taking DNA testing mainstream, and they now have the world’s largest autosomal DNA database. The test benefits from a number of innovative and sophisticated features such as shaky leaf DNA hints integrated with family trees, DNA Circles, Genetic Communities and New Ancestor Discoveries. A subscription is required to access some of these features and to view the full trees of your matches. The lack of a chromosome browser and matching segment data is a big disadvantage for advanced users who are interested in chromosome mapping. Many of the people now taking the AncestryDNA test are lured in by the biogeographical ancestry reports, but are not interested in communicating about genealogy. However, the test is encouraging an interest in genealogy in a subset of this market. Standard/sale prices Both companies offer reduced prices several times a year particularly around Thanksgiving/Christmas. Y-DNA tests are cheaper if you take a test through a research group. FTDNA ● Y-DNA 25 marker $109 37 marker $169 (currently $129) 67 marker $268 (currently $229) 111 marker $359 (currently $299) ● Mitochondrial DNA full sequence $199 ($169) ● Autosomal $89 (about £68)(currently $59/£45) Ancestry Autosomal £79+£20 p&p Y-DNA Testing 1 The Y-Chromosome is one of the 23rd pair of human chromosomes. Only males have a Y-chromosome, because women have two X chromosomes in their 23rd pair. A man's male-line ancestry, can be traced using the DNA on his Y chromosome (the Y-DNA), because the Y-chromosome is transmitted father to son nearly unchanged. A man's test results are compared to another man's results to estimate the number of generations in which the two individuals shared a most recent common ancestor, or MRCA, in their direct patrilineal lines. If their test results are very close, they are related within a genealogically useful time frame. Y-DNA Testing 2 Most of Y chromosome is very stable over very long periods of time but some areas “stutter” and a sequence of letters is repeated several times. Y-DNA testing looks at these repeating sequences called Y-STR = Short Tandem Repeats. These sequences are given names usually beginning DYS (DNA Y-chromosome segment) and a unique identification number. The number of times it repeats is the value of the marker, recorded as e.g. DYS 393 – 13 i.e. 13 repeats of a particular string. Occasional errors in copying mean this value changes very slowly over time. Y-DNA Testing 3 A Y-DNA result will be shared by thousands of men across the planet showing that you share a common ancestor with them. But if they don’t have the same surname then it is probably from before surnames came into use and therefore of no interest. Y-DNA tests look at a fixed number of specific sequences ranging from the historical 12 markers to modern 111 but more usually 37 or 67. Y-DNA Testing 4 The combination of numbers for all markers tested is called the Y-DNA Haplotype. The difference in marker numbers is called the genetic distance e.g. 1 if 36 of 37 markers match. Probability of common ancestor for distance 1 or 2 in 37 is as follows: Generation 4 8 12 16 20 24 28 Percent (1) 58.5 88.95 97.44 99.45 99.89 99.98 100 Percent (2) 28.94 68.67 89.14 96.71 99.08 99.76 99.94 Non-Paternity Events Sometimes a test will not match an expected family member, this is known as a non-paternity event (NPE). There can be many reasons for this including: ● faulty research ● Illegitimacy / paternity fraud ● use of an alias ● change of surname ● adoption Why did I do it? Kearton family Basil Kearton back to ? Ancestral origin Robert Kearton John Kearton of Kearton, 1200 (Kathy Sztanko) back Thwaite, b.