An Introduction to Forensic Genetics

Foreword ix Preface xi Preface to first edition xiii 1 Introduction to forensic genetics 1 Forensic genetics 1 A brief history of forensic genetics 2 References 6 2 DNA structure and the genome 11 DNA structure 11 Organization of DNA into chromosomes 11 The structure of the human genome 13 Genetic diversity of modern humans 15 The genome and forensic genetics 16 Tandem repeats 16 Single nucleotide polymorphisms 18 References 19 3 Biological material – collection, characterization and storage 21 Sources of biological evidence 21 Collection and handling of material at the crime scene 23 Identification and characterization of biological evidence 23 Evidence collection 29 Sexual and physical assault 31 Storage of biological material 32 References 32 4 DNA extraction and quantification 37 DNA extraction 37 General principles of DNA extraction 37 DNA extraction from challenging samples 41 Quantification of DNA 45 DNA IQ system 48 References 49 5 Polymerase chain reaction 53 The evolution of PCR-based profiling in forensic genetics 53 DNA replication: the basis of the PCR 54 The components of PCR 54 Taq DNA polymerase 54 The PCR process 56 PCR inhibition 58 Sensitivity and contamination 60 The PCR laboratory 60 Further reading 62 References 62 6 The analysis of short tandem repeats 67 Structure of STR loci 67 The development of STR multiplexes 67 Detection of STR polymorphisms 70 Interpretation of STR profiles 72 Further reading 77 References 77 7 Assessment of STR profiles 81 Stutter peaks 81 Split peaks (±N) 81 Pull-up 83 Template DNA 84 Overloaded profiles 84 Low template DNA typing 84 Peak balance 86 Mixtures 86 Degraded DNA 88 PCR inhibition 90 References 91 8 Statistical interpretation of STR profiles 95 Population genetics 95 Deviation from the Hardy–Weinberg equilibrium 96 Statistical tests to determine deviation from the Hardy–Weinberg equilibrium 97 Estimating the frequencies of STR profiles 98 Corrections to allele frequency databases 98 Which population frequency database should be used? 103 Conclusions 104 Further reading 104 References 104 9 Evaluation and presentation of DNA evidence 107 Hierarchies of propositions 107 Likelihood ratios 109 Two fallacies 113 Comparison of three approaches 114 Further reading 115 References 115 10 Databases of DNA profiles 117 The UK National DNA Database 117 International situation 124 Further reading 128 References 128 11 Kinship testing 131 Parentage testing 131 Punnett square 132 Identification of human remains 139 Further reading 140 References 140 12 Single nucleotide polymorphisms 145 SNPs – occurrence and structure 145 Detection of SNPs 146 SNP detection for forensic applications 148 Forensic applications of SNPs 149 SNPs compared with STR loci 150 References 152 13 Lineage markers 155 Mitochondria 155 Applications of mtDNA profiling 157 Haplotypes and haplogroups 159 The Y chromosome 161 Forensic applications of Y chromosome polymorphisms 162 Further reading 165 References 165 14 Non-human DNA typing 171 Non-human sample types 171 Species identification 173 Linkage to an individual using STR loci 174 Linkage to an individual using mitochondrial loci 175 Microbial DNA testing 176 Concluding comments 176 Further reading 176 References 176 Appendix A Forensic parameters 181 Appendix B Useful web links 183 Glossary 185 Abbreviations 189 Index 193