1. SNPs and the Human Genome Prof. Sorin Istrail

2. A SNP is a position in a genome at which two or more different bases occur in the population, each with a frequency >1%. GATTTAGATCGCGATAGAG GATTTAGATCTCGATAGAG Single Nucleotide Polymorphism (SNP) The most abundant type of polymorphism The two alleles at the site are G and T

3. tttctccatttgtcgtgacacctttgttgacaccttcatttctgcattctcaattctatttcactggtctatggcagagaacacaaaatatggccagtggc ctaaatccagcctactaccttttttttttttttgtaacattttactaacatagccattcccatgtgtttccatgtgtctgggctgcttttgcactctaatggcag agttaagaaattgtagcagagaccacaatgcctcaaatatttactctacagccctttataaaaacagtgtgccaactcctgatttatgaacttatc attatgtcaataccatactgtctttattactgtagttttataagtcatgacatcagataatgtaaatcctccaactttgtttttaatcaaaagtgttttggcc atcctagatatactttgtattgccacataaatttgaagatcagcctgtcagtgtctacaaaatagcatgctaggattttgatagggattgtgtagaat ctatagattaattagaggagaatgactatcttgacaatactgctgcccctctgtattcgtgggggattggttccacaacaacacccaccccccac tcggcaacccctgaaacccccacatcccccagcttttttcccctgctaccaaaatccatggatgctcaagtccatataaaatgccatactatttgc atataacctctgcaatcctcccctatagtttagatcatctctagattacttataatactaataaaatctaaatgctatgtaaatagttgctatactgtgtt gagggttttttgttttgttttgttttatttgtttgtttgtttgtattttaagagatggtgtcttgctttgttgcccaggctggagtgcagtggtgagatcatagctt actgcagcctcaaactcctggactcaaacagtcctcccacctcagcctcccaaagtgctgggatacaggtgtgacccactgtgcccagttatt attttttatttgtattattttactgttgtattatttttaattattttttctgaatattttccatctatagttggttgaatcatggatgtggaacaggcaaatatggag ggctaactgtattgcatcttccagttcatgagtatgcagtctctctgtttatttaaagttttagtttttctcaaccatgtttacttttcagtatacaagactttg acgttttttgttaaatgtatttgtaagtattttattatttgtgatgttatttaaaaagaaattgttgactgggcacagtggctcacgcctgtaatcccagca ctttgggaggctgaggcgggcagatcacgaggtcaggagatcaagaccatcctggctaacatggtaaaaccccgtctctactaaaaataga aaaaaattagccaggcgtggtggcgagtgcctgtagtcccagctactcgggaggctgaggcaggagaatggtgtgaacctgggaggcgg agcttgcagtgagctgagatcgtgccactgcattccagcctgcgtgacagagcgagactctgtcaaaaaaataaataaaatttaaaaaaag aagaagaaattattttcttaatttcattttcaggttttttatttatttctactatatggatacatgattgatttttgtatattgatcatgtatcctgcaaactagct aacatagtttattatttctctttttttgtggattttaaaggattttctacatagataaataaacacacataaacagttttacttctttcttttcaacctagactg gatgcattttttgtttttgtttgtttgtttgctttttaacttgctgcagtgactagagaatgtattgaagaatatattgttgaacaaaagcagtgagagtgg acatccctgctttccccctgattttagggggaatgttttcagtctttcactatttaatatgattttagctataggtttatcctagatccctgttatcatgttga ggaaattcccttctatttctagtttgttgagattttttaattcatgtgattgcgctatctggctttgctctca tctc gaga gaga gaga gaga gaga gcgc gcgc gcgc tctc gaga gaga gaga gaga gaga tctc tctc tctc tctc gaga gaga gaga tctc gcgc tctc tctc tctc Human Genome contains ~ 3 G basepairs arranged in 46 chromosomes. Two individuals are 99.9% the same. I.e. differ in ~ 3 M basepairs. SNPs occur once every ~600 bp Average gene in the human genome spans ~27Kb ~50 SNPs per gene

4. G C T C G A C A A C A G G T T C G T C A A C A G Two individuals C A G Haplotypes T T G SNP Haplotype

5. Mutations Infinite Sites Assumption: Each site mutates at most once

6. Haplotype Pattern 0 0 1 1 0 1 0 0 1 0 0 1 C A G T T T G A C A T G C T G T At each SNP site label the two alleles as 0 and 1. The choice which allele is 0 and which one is 1 is arbitrary.

7. G T T C G A C T A T T A G T T C G A C A A C A T A C G T A T C T A T T A Recombination

8. G T T C G A C T A T T A G T T C G A C A A C A T A C G T A T C T A T T A The two alleles are linked, I.e., they are “traveling together” ? Recombination disrupts the linkage Recombination

9. Variations in Chromosomes Within a Population Common Ancestor Emergence of Variations Over Time timepresent Disease Mutation Linkage Disequilibrium (LD)

10. Time = present 2,000 gens. ago Disease-Causing Mutation 1,000 gens. ago Extent of Linkage Disequilibrium