Your Family 101 Beginning Genealogical Research

Transcription

1 Your Family 101 Beginning Genealogical Research

2 What Will We Cover Today? Session 1: Getting Started Session 2: Your Resources Session 3: Common Mistakes and Pitfalls Session 4: DNA Testing and Medical Pedigrees Basic Genetic Inheritance What do the tests do/not do? The Testing Companies Medical Pedigrees Session 4: Presentation and Collaboration

3

4 (Very) Basic Genetics DNA, the building block of life, is packed into each human cell Each length of a DNA sequence that specifies a feature of your body is called a gene (we have about 30,000 to 40,000 genes that give instructions for human bodies) DNA in a cell is packed into bundles called chromosomes

5 (Very) Basic Genetics We each have 23 pairs of chromosomes (total of 46) Numbered 1-22, with the remaining pair called X or Y If you are a woman, you are XX; if you are a man, you are XY You received one set of 23 chromosomes from your mother, and one set from your father

6 The Box of Records Imagine your ancestor has a wooden chest of genealogical records from his parents and grandparents and great-grandparents. Analogy courtesy of Diahan Southard of The National Institute for Genealogical Studies

7 The Box of Records He makes copies of everything, then divides the copies of his collection into separate boxes in a totally haphazard fashion: Census records, land deeds, birth certificates, family bibles, etc. from BOTH sides of his family are mixed together in each box.

8 The Box of Records Each box winds up containing about half of the records, and each of his children receives a different box.

9 The Box of Records Each child received a box from their father and a similar box from their mother; the daughter, Suzy, opens both of her boxes and dumps all of the records together in a new box.

10 The Box of Records Suzy and her husband recreate the entire process to pass records along to their children.

11 The Box of Records And so on, through the generations until you! Now you have a box containing records from both parents and their parents and their parents and their parents trying to figure out which record came from which ancestor on which side of the family.

12 The Box of Records BUT YOUR SIBLINGS did not get the same mix of records that you did! They may have some of the same records, they may have many different records. But they also got about half of their records from Mom and about half from Dad.

13 A Little Simple Math About what percent of their DNA does a child inherit from each parent? About what percent of their DNA, then, comes from each grandparent? Great-grandparent? 50% 25% 12.5% Great-great-grandparent? 6.25% Great-great-great-grandparent? 3.125%

14 On average, you will share about * *Unless you re endogamous More about that shortly.

15 What about ancestors before that? That box of records is stuffed pretty full already so in every generation, some of those old records that just won t fit in the box anymore are going to get thrown away. You reliably carry DNA from each of your ancestors back through your 3X great-grandparents. Before that, though, parts of your heritage will have disappeared, because those records just won t fit in the box!

16 Types of Tests Autosomal DNA Test Mitochondrial DNA Test (mtdna) Y-chromosome DNA Test (YDNA)

17 Autosomal DNA The two boxes of records you got from each of your parents Inherited from the autosomal chromosomes Any of the 22 numbered chromosomes (not the sex chromosomes) Anyone (man or woman) can take an autosomal DNA test

18 Mitochondrial DNA Different kind of DNA Not found in the nucleus of the cell with the other 46 chromosomes; floats out in the cell s cytoplasm Passed down from a MOTHER to all of her CHILDREN (anyone can take the test) Traces the direct maternal line

19 Y-chromosome DNA Stands as a perfect and complete record of a direct paternal line (mutates very rarely) Only inherited from FATHER, only passed to SONS (because women don t have Y-chromosomes) So only men can take this test Women: If you want this information, test your brothers, or your father, or his brothers

20 The Tests CAN: Help you find genetic relatives who have taken the test, both closely related and distantly Give you a basic breakdown of the ethnicities reflected in your DNA*/Tell you what parts of the world some of your ancestors may have come from Inform you of potential medical issues related to your genetic inheritance (23andMe only) Tell you things you MIGHT NOT want to know so consider carefully before you take the plunge! *We ll discuss this more in a moment

21 The Tests CANNOT: Do your genealogy research for you Give you a 100% accurate picture of your ancestral ethnicities or heritage Why not? 1) 2) 3) 4) You don t carry DNA from all of your ancestors The tests cannot account for human migration Admixture test results rely on living people/dna to extrapolate Very small percentage results (>1%) are likely statistical noise

22 Endogamy The practice of intermarrying within a limited/isolated group over an extended period of time Endogamous cultures/societies include: Eastern European Jews, Mormons, Amish/Mennonites, Finnish, Cajuns, people from Newfoundland, Indian castes, people from small island nations

23 What are the implications of endogamy for DNA research? Let s look at an extreme example to understand

24 Looks a bit snug. Mom

25 What are the implications of endogamy for DNA research? The same people will have shown up more than once in your family tree, occupying different spots You share more DNA with their descendents than your actual relationship to them would predict Therefore: 1) 2) 3) The algorithm will tell you that you are more closely related to a person than you are (ex. 3 rd -5 th cousin is actually 5 th -7 th [ish]) You ll have hundreds of DNA Relatives who are only negligibly related to you It s more difficult to figure out whether a person is from your maternal or paternal side (since they could be from both) Long story short: the autosomal testing will be less reliable and much more frustrating but not impossible.

26 The Testing Companies 23andMe AncestryDNA FamilyTree DNA

27 23andMe Offers autosomal testing (ancestry reports, DNA relative prediction and messaging system), traits and wellness reports, genetic health risk reports, carrier status reports Health + Ancestry Kit: $199 Ancestry Only Kit: $99

28 AncestryDNA Offers autosomal testing (ancestry report, DNA relative prediction and messaging system, access to public member trees) Ancestry Kit: $79

29 FamilyTreeDNA Offers autosomal testing (ancestry report, DNA relative prediction and messaging system), mdna testing, YDNA testing Family Finder (autosomal) kit: $89 mtfull Sequence (mdna) kit: $199 Y-37 (YDNA) kit: $169 Test Bundles: varying prices

30 COMPARISON FamilyTreeDNA AncestryDNA 23andMe Database Size 500,000 people 4 million people 2 million people Strengths Most types of tests; best for the serious genealogist Largest collection; most user-friendly (leaf system) Medical/health DNA screening Weaknesses Not user-friendly for beginners No way to verify potential matches; US-centric; some trees private Matches often don t respond; limited family tree support Contact Relatives Yes name and provided Yes username provided; message through internal system Yes username provided; message through internal system Reveal Ethnicity Yes best for non- European ancestry Yes, but less precise than the others Yes best for European ancestry

31 Which Company Should I Test With? If you re most interested in Ethnicity Estimates: 23andMe for European heritage, FTDNA for non- European heritage If you re most interested in testing your YDNA or mtdna: FamilyTreeDNA If you want to be connected to relatives: AncestryDNA If you re most interested in health/medical issues: 23andMe

32 Medical Pedigrees Why would you do this? To trace and track specific traits within your family To determine if there are any concerning patterns of illness/ailments that should be discussed with a doctor

33 Drawing a Pedigree Chart You ll need at least three generations worth to start recognizing real patterns.

34 Patterns ( Modes ) of Inheritance Patterns describe how a disease or traits is transmitted in families Dominant One mutated copy of the gene in the gene pair will cause the mutant trait to appear in the inheritor Recessive Both copies of the gene in the pair must carry the trait for it to appear in the inheritor A person with only one copy of the mutant gene is a carrier X-linked Due to a mutated gene on the X-chromosome (from your mother) Can act in either a dominant or recessive manner

35 Dominant One or both parents are always affected 50% chance for each child to be affected Both sexes equally affected All generations are affected Unaffected children will not be carriers Ex. Huntington disease, Marfan s syndrome, myotonic muscular dystrophy

36 Dominant Example

37 Recessive Can skip generations due to the presence of carriers Trait occurs equally in males and females If both parents are carriers, 25% chance for each child to be affected If one parent is a carrier, none of their children will be affected, but each will have a 50% chance of being a carrier him/herself Ex. Sickle cell anemia, cystic fibrosis, albinism Recessive diseases show up more often in consanguineous relationships (related by blood)

38 Recessive Example

39 X-linked If the trait acts recessively, approximately half of males and no females will be affected Also, if it acts recessively, it can skip generations If the trait acts dominantly, approximately half of males and half of females will be affected Appear more often in males because if a man receives a bad X-chromosome variant from his mother, he doesn t have a chance of getting a good X variant from his father to hide it No father-to-son inheritance will be seen Ex. Hemophilia, Red-green color blindness

40 X-linked Example

41 X-linked vs. Autosomal If most of the males in the pedigree are affected, then disorder is x-linked If it s about a 50/50 ratio between men and women, then disorder is autosomal

42 Ethics 1) A medical pedigree is a medical record, regardless of the qualifications of the compiler 2) No person should be wrongfully included on, or excluded from, a medical pedigree 3) Confidentiality or disclosure should not cause harm

43 Getting Started Two approaches: Begin with a specific trait/disorder in mind First, find out every detail associated with that trait, and then seek out those details among ancestors and relatives Ex. Looking for pancreatitis, noted relatives diagnosed with that disorder, those with similar pains, and those who had diabetes (which often develops) Intend to uncover any and all traits possible during the course of general family history research Collect information, transcribe, but do not add your own interpretations (patterns may become apparent only with all possible information faithfully assembled) Find a thorough medical dictionary to help you interpret the archaic words/phrases you might come across in the records

44 Clues can be found Besides the obvious death certificates or medical records and besides talking to relatives, which I m sure I don t need to tell you to do! Letters and diaries might discuss an ancestor s illnesses School report cards might mention illness or learning difficulties Photographs might reveal genetic disorders in a person s face or body, or other physical characteristics Burial records or obituaries may include information on cause of death Some census records or immigration forms may include information on infirmities

45 Look for: More than one sibling showing the same trait or group of traits More than two generations showing the same trait or group of traits Diseases being diagnosed and/or causing death at an unusually young age; any occurrence of severe genetic diseases Anything that you feel uneasy about