front 1 What are STRs? | back 1 (short tandem repeats) -usually 2-6 bp repeating DNA motifs -highly polymorphic Co-dominant inheritance located in non-coding regions |
front 2 How and why are STRs used in forensic science? | back 2 -High discriminatory power -standardized loci sets -works with small or degraded DNA -Produces a numerical DNA profile for comparsion |
front 3 What are the different classes/type of STRs? | back 3 -Simple: single repeated motifs -compound: two adjacent motifs -complex: repeats with internal vatiations - by length: di-, tri-, tetra- |
front 4 How does multiplex amplification work? | back 4 -Amplifies many STR loci at once - Uses multiple primer pairs and different fluorescent dyes -Requires careful primer design to avoid overlap/dimers |
front 5 How are STRs used for identification? | back 5 -compare alleles across multiple loci - A full profile has extremely low probability of being duplicated -used to confirm or exclude contributors - each person has a unique combination of STR alleles -STR profiles are generated via capillary electrophoresis and compared to a reference sample or databases -match probability is calculated using allele frquencies |
front 6 Be able to calculate RMP given an electropherogram | back 6 -RMP product of genotype frequencies -For heterozygotes: 2pq -For homo: p^2 Multiply loci get overall RMP |
front 7 Be able to describe how RMP is presented in court room | back 7 "The probability of two selected individuals having this profile is 1 in X" - helps convey the strength of the DNA match to the jury |
front 8 What are the different types of mixture analysis? | back 8 -qualitative: number of contributors, major/minor -quantitative: estimating contributor ratios -peak height analysis: relative contributor proportions - statistical: likelihood ratios, probabilistic genotyping |
front 9 Describe the different primer characteristics that contribute to PCR amplification? | back 9 -similar melting temps -40-60% GC content -high specificity - Avoid hairpins, self dimers, cross-dimers -short enough for degraded DNA |
front 10 How do you design a successful primer pair? | back 10 -Flanking target region, matching melting temperature, little complementarity, correct product size for multiplex - Target conserved flanking regions -Avoid repetitive or homologous sequencing -Use software to optimise Tm, GC content, and specificity - Validate with in silico PCR and empirical testing |
front 11 What are the 2 types of DNA found in the cell? compare and contrast nuclear DNA and mtDNA (nuclear DNA difference) | back 11 Nuclear DNA: - inherited from both parents - Location: nucleus - highly individualizing -linear - diploid, low copy number -used for STR profiling |
front 12 What are the 2 types of DNA found in the cell? compare and contrast nuclear DNA and mtDNA (mt DNA differences) | back 12 mtDNA: - maternally inherited -obtained from mitochondria - circular shape - high copy number-> survives degradation - Not as discriminating -used for degraded samples and maternal lineage - more likely to have mutations |
front 13 Why and when is mtDNA used in a forensic context? | back 13 - works when mtDNA is too degraded or absent - Useful for hair shafts, bones, burned or old samples, maternal lineage tracing, missing persons |
front 14 What is the HVI/II region? | back 14 -hypervariable regions of mtDNA control region - most polymorphic parts-> best discrimination -used for lineage tracing and degraded samples |
front 15 How is mtDNA obtained? | back 15 1. collect sample 2. lyse open cells 3. DNA extraction 4. Amplification 5. Sequence the amplified mtDNA 6. compare to databases |