Summary of concepts Human DNA Analysis and Interpretation
This document contains keywords for concepts of which an expert in the field of DNA should minimally have a basic knowledge.
Forensic biology
- Sources of DNA evidence
- Crime scene investigation and laboratory analysis of biological evidence
- Identification and presumptive testing of body fluids (blood, semen, saliva)
- Confirmatory assays for body fluid identification (immunoassays)
- Uncertainty concerning attribution of DNA (particularly at low levels) to specific body fluids
General
- The structure of DNA and the variability of the human DNA genome
- Loci, alleles, genotypes and DNA profiles
- Polymorphisms commonly used for DNA testing
- The molecular biological basis of forensic DNA tests; using the DNA profile to identify a forensic sample
- Extraction and quantification of DNA
- Polymerase chain reaction
- Short tandem repeats and mutation processes
- Forensic multiplex STR typing kits
- DNA separation by CE and LIF detection
- Analysis of results, including the use of ladders for fragment sizing, use of analytical thresholds and identification of artefacts such as stutter, “pull-up” and identification of mixed samples.
QC/QA
- Quality control and quality assurance of forensic DNA analysis
- Laboratory accreditation, personnel certification and proficiency testing
- Validation studies
- Laboratory error rates
- Understanding and minimizing the risk of contamination in the forensic process: methods of reducing the occurrence of contamination and detecting when it has occurred
- Continuous improvement and quality
DNA statistics
- Likelihood Ratio (LR)
- Bayes Theorem
- Product rule to calculate the probability of independent variables
- DNA mixture deconvolution and recommended procedures for analysing mixed samples
- Accounting for relatives, where applicable, in calculating evidential strength
- Database issues
- Inclusion criteria and search (im)possibilities of the national DNA database including the detection of false negative and false positive matches
- Population Genetics
- Hardy-Weinberg equilibrium/Linkage equilibrium
- Population Substructure
- Allele frequencies, genotype probabilities
- Applying the product rule for independent events
- Conditional match probabilities
- Fst/Theta population substructure correction; correction for possible allele dropout
- Sampling variation in construction of DNA population databases
- Proper Interpretation of the Evidence
- Common Logical Fallacies (Prosecution/Defence Fallacy)
- Evidential strength of database match
- DNA database search controversy
- Avoidance of cognitive bias
Minimal traces (Low Template DNA Analysis)
- Evaluation of potential low template DNA typing results.
- Allele and/or locus dropout due to degradation, preferential amplification, stochastic effects and stochastic thresholds
- Replication and consensus DNA profiles
- Approaches for the statistical evaluation of DNA profiles from low template DNA samples
Y-chromosome Testing
- Y-chromosome evolution and its consequences for forensic analyses
- Patrilineal inheritance
- Laboratory analysis of Y-chromosome STR’s
- Population genetics of Y-STR haplotypes
- Use of Y-STR population databases (YHRD)
- Statistical evaluation of Y-chromosome haplotypes
- Interpretation of Y-STR mixtures
Kinship DNA Testing
- Inheritance of genetic polymorphisms
- Technical procedures for determining kinship
- Statistical evaluation of kinship (e.g. paternity index, sibling index, Bayesian networks)
- Incorporation of the presence of mutations and null-alleles in the statistical evaluation
- Principles of disaster/mass identification
- Principles of familial searching in databases
- Use of Y-STR and mtDNA analysis to narrow candidate lists from familial searching in databases
Externally Visible Characteristics
- Evolution and migration of Homo sapiens
- Population genetics of externally visible characteristics
- Principles of determining the geographic origin of an individual
- Principles of determining externally visible characteristics
- Knowledge about genes involved in the biosynthesis of melanine (skin and hair pigmentation, iris colour)
- Technical procedures for determining geographic origin or externally visible characteristics
- Approaches for the interpretation of genotyping results for determining geographic origin or externally visible characteristics
- Knowledge of the limitations of determining geographic origins or externally visible characteristics
Mitochondrial DNA Testing
- Mitochondrial DNA evolution and its consequences for forensic analysis
- Matrilineal inheritance, variable mutation rates, heteroplasmy and principles for evaluating close non-matching mtDNA sequences
- Laboratory analysis of mitochondrial DNA (e.g. Sanger sequencing, mini-sequencing)
- Population genetics of mitochondrial DNA haplotypes
- Use of mitochondrial DNA databases (EMPOP)
- Statistical evaluation of mitochondrial DNA matches
Reporting at Activity level
- Understanding of the principles of case assessment and interpretation (CAI)4 and the necessity for the following criteria: balance, logic, robustness and transparency
- Formulation and evaluation of appropriate hypotheses
- Understanding use of data and experience for evaluation of results given activity level hypotheses:
- Knowledge concerning transfer of cells and DNA (primary, secondary, tertiary)
- Knowledge concerning persistence of DNA and the impact of e.g. environmental conditions
- Extensive experience of forensic DNA analysis and interpretation in forensic casework
- Transparency regarding any limitations of the data used - Understanding of the principles of probabilistic (Bayesian) networks in evidence interpretation