DNA I Lecture Notes - FRSC2030H (PDF)

DNA I LEC12 Monday October 27th FRSC2030H Foundations in Forensic Science  Test I LAB03 Anthropology 50% in lab portion Course Update 50% post-lab assignment LAB04 Forensic Entomology Bri...

DNA I LEC12 Monday October 27th FRSC2030H Foundations in Forensic Science  Test I LAB03 Anthropology 50% in lab portion Course Update 50% post-lab assignment LAB04 Forensic Entomology Bring notebook & calculator Case Study – O.J. Simpson June 12th 1994 Nicole Simpson and Ron Goldman found dead on path home Mountain of DNA Evidence Blood stains lead away from the scene OJ’s profile Blood stains in OJ’s home’s driveway OJ’s profile Blood droplets in OJ’s home’s foyer OJ’s profile Blood stains in OJ’s Ford Bronco OJ, Nicole and Ron’s profiles Blood-soaked sock in OJ’s bedroom Nicole’s profile Bloodstained glove outside OJ’s residence Nicole and Ron’s profiles Acquitted of murder Brief History Kary Mullins - PCR 1983 Invented polymerase chain reaction Alec Jeffreys - DNA fingerprinting 1984 Examining X-rays of DNA from lab technicians Realized differences and similarities could be compared 1985 Immigration case Young boy with parents from Ghana Colin Pitchfork case 1989 Microsatellites/STRs 1994 CODIS 2018 update Collection 1. Is it what it looks like? 2. What species? 3. Who was donour? Most common types: Blood, semen, saliva, other bodily fluids How to answer #1? Presumptive testing Can indicate if it may be a type of biological material or if it is definitively not Confirmatory testing Can identify specific biological material Collection of Semen Acid Phosphatase test AP 400 times more present in semen Fast Blue B Prostate-Specific Antigen (PSA) p30 Also present in low levels in other tissue Antibody-antigen “sandwich” Reactive = PSA present Microscopic ID Immersion in water, transfer to slide, examine Collection of SAEs Must be carefully collected Needs to be collected soon after assault Victim: Reference samples Pubic combing, external/internal genilal swabs, rectal swabs, oral swabs, sawbs of specific other areas, blood & urine samples, fingernail clippings, all clothing Timing Sperm motility PSA detection Deoxyribonucleic Acid (DNA) Double helix structure Egg/Sperm Zygote Heredity Chromosomes Genes Locus Allele Homozygous Heterozygous Basic Structure Nucleotides (G,T,A,C) Polymerase Chain Reaction (PCR) Forensic cases have low DNA volumes DNA Polymerase Enzymes “proofreading” Cycles Unwind DNA Split DNA Assemble negative/positive Restart Polymerase Chain Reaction (PCR) DNA Double Helix DNA unwound & split 94°C Primers anneal 60°C DNA assembled 72°C DNA Typing Sections of the Genome are repeated Many over 30 times Over 30% of genome repeats “tandem repeats” Short tandem repeats (STRs) Most widely used DNA-profiling procedure Locations (loci) on genome which repeat 3 to 7 bases repeated