3/31 Using DNA to Track Your Ancestors

Transcription

1 1/9/16 11:49 AM 3/31 Using DNA to Track Your Ancestors DNA analysis: General Procedure (slide 1) Amplify sections of the DNA Separate DNA fragments by length and visualize Compare the DNA pattern between two individuals Types of DNA analysis (slide 2) Compare sequenced genomes (Slide 3) o Architecture

2 o Dependent on methods o Finding orthologs o rrna gene Scientists use DNA to trace Life s Time line Time Tree compare last common ancestor between two species o Genomics advances o Rapid DNA sequencing o Ability to compare genomes o Ability to compute evolutionary distance from sequence changes (Allan Wilson) o Statistical advances o Baysian probabilities o Markov paths Microsatellite Regions Tandem repeated DNA motifs that range in length from two to five nucleotides, and are typically repeated 5-50 times

3 TATATATATA Dinucleotide repeat/ 5 times Neutral regions-fix mutations Replication slippage changes repeat number 1/1000 replications PCR amplification (slide 3) Amplifying DNA by PCR Using two primers that bracket a particular microsatellite, or VNTR, sequence produces a different pair of DNA bands from each individual.

4 One bands contains the repeated VNTR sequence from the individual's mother and the other from the individual's father. DNA bands obtained from a set of different PCR reactions each of which amplifies the DNA from a different VNTR sequence "fingerprint" to identify each individual nearly uniquely. The starting material for the PCR reaction can be a single hair that was left at the scene of a crime. Single nucleotide polymorphisms (Slide 4) Change of a single base (variation) at a known location o 8.8 x 10 5 SNPs/ 2.7 x 10 9 bp in human DNA Detected on SNP chips

5 o An array containing immobilized allelespecific oligonucleotide (ASO) probes. o Fragmented nucleic acid sequences of target, labeled with fluorescent dyes. o A detection system that records and interprets the hybridization signal. o Ancient hominid DNA-Whole DNA approach (Slide 6)

6 o Homo heidelbergensis-ancestor of H.neanderthal,H.denisova, and H. sapiens o New species yet to be discovered Neanderthal and Denisovan % of genome Haplogroups (Slide 7) Defined by a unique SNP Haplotypes Identical mutations within the Haplogroup

7 Eve and her 7 Daughters (Slide 8) Mitochondrial Eve:matrilineal most recent common ancestor (MRCA) of all currently

8 living humans o mtdna inherited by both male and female offspring o lived between 99,000 and 200,000 years ago,most likely in East Africa Alan Wilson (molecular clock) 1986 mt work

9 o Post-doc Wesley Brown-Mutation in mtdna is fast 1%/million years Large variation among human subjects o Grad student Rebecca Cann Collected mt DNA based on ethnicity (100 samples)

10 o Grad student Mark Stoneking Collected mt DNA samples from aboriginal Australians New Guineans and!kung o All current mtdna derived from a specific women in East Africa Common misconceptions o Not the only women o Not a fixed individual over time o Not necessarily a contemporary of Y chromosome Adam o Not the most recent ancestor shared by all humans Human MRCA 5000 years ago ú A few thousand years before MRCA, all humans then alive left no descendants alive today or were common ancestors of all

11 humans alive today (identical ancestor point) each present-day human has exactly the same set of genealogical ancestors" alive at the "identical ancestors point" o Not the biblical eve Y-chromosome Adam (Slide 9) Almost all males inherit Y chromosome from a single male

12 o Lived 200,000 years ago Emergence of anatomically modern H. sapiens Lived before Eve Lived in North-west Africa Both Y and mt studies support out of Africa Hypothesis Commercial Genealogy Companies (slide 10) Services available 111 segments of your Y chromosome Some or all of your mitochondrial DNA Most of your 22 non-sex chromosomes (1 million markers) Ancestory.com Originally Sorenson Molecular Genealogy Foundation (1999) Started by a Mormon billionaire to look at DNA from Norway

13 Associated with the Mormon family History Centers-Giant database of genealogy data Collected DNA from Norway, Africa, Asia, Kyrgyztan, Mongolia greater than 100,000 samples Acquired by ancestory.com (2112) Documented lineages of more than 700,000 sites on the genome including mtdna and the Y chromosome Family Tree DNA(2000) Bennett Greenspan based on two genetics cases in media of shared Y chromosome Male descendants of Thomas Jefferson and Sally Hemings Many Cohen males of Ashkenazic and Sephardic origin (Cohen Modal Haplotypehaplogroup J) Diaspora marker for descendants of Aaron

14 Appears in other haplotypes not associated with Cohen Multiple lineages among Cohen Y-chromosome Levi (son of Jacob) Haplogroup E1b1b1 common in Eastern Europeans Haplogroups J1 and 2 and E1b1b1 are prevalent among Jewish populations Samaritan Cohens Distinct religious and cultural sect Broke away from mainstream Jews in 5BCE Maintain extensive genealogical records Belong to haplogroup E1b1b1 All crowd sourced Family Tree DNA largest collection of mt and Y chromosome data What genealogical information is written in the DNA (TheGeneticGenealogist.com YourGeneticGenealogist.com)

15 Place of origin Religious origins Geographic origins Adoptees to find families Baby switches in hospitals Abandoned infants Genetic based social networks Companies track genetic cousins and specific segments of the genome o Alert customers to large shared segments-identity by descent o Trace back from autosomal DNA 5 generations o Identify 3d cousins 90% prob o 4 th cousin with 50% prob o 5 th cousin with 10% prob o documented examples of 8 th cousins

16 o Large enough group of descendants in a single family line, rebuild the genome of the group s common ancestor o Theoretically, rebuild the population of a city in 1850