5. DNA

5. DNA Forensic DNA Nitrogenous Bases • Adenine (A) • Thymine (T) • Cytosine (C) • Guanine (G) ] ] • Sugar Phosphate Backbone Transfer of Biological Fluids Identification: Blood, Saliva Individualization: Determine source through DNA analysis Forensic Science Compares Unknown to Unknown DNA Applications Unknown to Known • Medical Research, Gene Therapy People, Places, Objects • Cloning, Gene Engineering Inclusions or Exclusions • Paternity Testing • Missing Persons, Body Identification Types of Evidence • Biological Warfare Detection Systems • Human Evolution Studies • Human Genome Project • Forensic Science Clothing Chewing Gum Weapons Cigarette Butts Stamps/Envelope Bottles s Fingerprints 2 Types of DNA Biological Sources From Evidence • Blood (White Cells Only) • Red:White = 400:1 • Roots of Hair • Bone • Teeth • Epithelial Cells (Saliva, Skin) Nuclear DNA (nDNA) ~3 billion base pairs STR testing Mitochondrial DNA (mtDNA) ~16,600 base pairs mtDNA testing Short Tandem Repeats (STR) • Small regions along the DNA chain where a particular sequence of bases repeat consecutively. • The number of repeats in a region can vary from person to person. Analytical DNA • 20 different DNA locations are analyzed as part of a DNA profile. • Known as STRs and have no known function. • Profiles do not include DNA for any visible traits (e.g. race, eye/hair color, diseases). Testify • DNA Match: The Frequency of Occurrence of that DNA is so low that the probability of it being someone else barely exists. DNA Profile Generator • Extraction of DNA from samples • Quantification: Is there enough DNA for testing DNA Amplification • Polymerase Chain Reaction (PCR): Makes millions of copies of each STR. • Each STR is labeled with a fluorescent blue, green or yellow dye. • Electrophoresis: The length of each STR is measured to determine the number of repeats. Equipment • Thermo-Cycler: Copies DNA • Gel Electrophoresis: Sizes DNA Fragments Interpretations & Comparisons • Profiles within a case (same source?) • Profiles between cases (pattern?) • Profiles to known victim/suspect exemplars (inclusion/exclusion?) An STR Profile in an Assumed 2 Person Mixture 2863-016-0429- Simple Mixture Deduction • You can deduce the profiles of the contributors of a mixture if: • You know how many contributors you have. • You have a comparison sample for one of those contributors. • One of the contributors is the major DNA donor to the sample. • Sometimes even with a comparison sample you can’t deduce a mixture when: • There are more than two contributors to the sample. • The known contributor shares many alleles with the unknown contributors. • There is no clear major DNA donor. Complex Mixtures • Sometimes the only conclusion you can make is: “PCR DNA testing was done on the following sample; the results show mixtures of DNA. The DNA profiles of the individual donors could not be determined.” DNA Missing Persons • Formed in 2004 as an offshoot of the work performed on September 11, 2001. • Since 2004, this group has worked on over 1,000 cases of unidentified, tentatively identified, and missing person cases. Identification Process • NYPD Missing Persons Fingerprints • Dental • Radiology (X-Ray) • Forensic Anthropology • DNA • Identification Unit • Medical Examiner Tissue Inside a Paraffin Block Direct Matches it"https://www.geneticistinc.com/blo • Compare DNA profile from Postmortem Item (PM) to DNA profile from Medical/Known Specimen of individual. • Freeze sample; Paraffin Block - Preserve Evidence Kinship Cases • Compare DNA Profile from Postmortem Item to DNA profiles from Buccal (Inside Cheek) Swabs from Relatives to see likelihood of genetic relationship High Sensitivity Low Copy DNA Testing • To identify DNA Bind Victims Touched Clothing Requirements contributors to challenging Cord Victim Exemplar biological samples which Laces Knowledge of area where may be degraded, Rope inhibited, or of a minute Wire Neck of shirt quantity using reliable, Zip-ties Right wrist clothing was touched state of the art technology. Head of jacket Buccal Swab High Sensitivity Testing • < 100 pg of DNA (16 cells) testing/"https://dnacenter.com/ • 1 pg = 10-12 g • 1 Paperclip ≈ 1 g • 1 Cell ≈ 6 pg DNA A Sample Triage • Low Template • Comprised Samples • Touched Objects • Skin (Epithelial Cells) Deposited on Samples • Handled Samples • Weapons, Tools, Wallet • Single Contact Samples • Window Sill, Door Knob Weapons • Guns: Handle, Trigger, Magazine, Bullet • Baseball Bat • Knife • Screwdriver High Template Body Fluids Rich in DNA Βlood Semen Saliva Tissue Bone • Metal Pipe • Scissors Swabs • Cotton: Sample stays entrapped in fiber want. • Flocked: Sample is released quickly and in higher amounts. Focus Touch DNA Recovery Swab Cotton vs Flocked Swab (Dry) • Neither has to be dried nor requires special storage. • SIM Buffer Solution: Antimicrobial & Anti-bacterial 0.1111/j.1556- • Preservative to protect & preserve recovered DNA Cleaning • Work surfaces & instruments cleaned with each use. • Bleach solution (made fresh with each use) • Water & 70% ethanol • Air dry • Irradiated in Stratalinker 2400 Cotton vs Flocked Swab (Wet) • UV Irradiation degrades DNA sufficiently so that DNA testing is not feasible. YfkH2wSw"https://www.youtube.com/w • At OCME, all plastic-ware, instrumentation, swabs, water and many buffers. Swabbing for DNA Analysis 1. Moisten a clean, sterile swab with 3-4 drops of sterile water. 2. Swab area to be tested. • For revolvers/semi-automatic handguns: Grip, trigger, hammer UV Stratalinker 2400 • For long guns: Buttstock, trigger areas, hand guard (forward grip) 3. Use different swabs for each area tested. Preferred Post-Mortem Samples 1. Non-Clotted Blood 3. Red Muscle Tissue (Deep) 4. Bone (Compact) Preferred Reference Samples Medical/Known Specimens Family Members Personal Item 5. Any Muscle Available 6. Any Bone Available Family Reference Samples Medical/Known Specimens • Biopsy Samples (Paraffin Embedded Tissue) • Blood (Bone Marrow Donor Program) • Pap Smear Specimen • Sperm Bank Samples Buccal Swabs from Parents, Children, Siblings At Least 2 Family Members Preferred Family Members • Baby Teeth • Dried Umbilical Cord Both Parents All Children/Spouse All Full Siblings Personal Items • Issues: Item taken from where body was found such as an apartment. • Prone to mixtures. NamUs.gov • Launched in 2007 as Unidentified Decedent Reporting System. • Missing persons component added in 2008. • Two-way searches enabled in 2009. • Accessible to MEs, law enforcement, and the general public. • Cases range from 1998 to present. • Coordinate to ensure within agency dental, anthropology, DNA, metadata are all complete. Exhumation From Potter’s Field (NYC) • Coordination with Department of Sanitation and Department of Corrections for ~30 unidentified human remains so far under 2009 NIJ award Combined DNA Index System (CODIS) • Collection of DNA profiles from convicted offenders. • Three Houses: Convicted Felons, Unidentified Persons, Profiles Generated from Crime Scenes. • Nationwide comparison of DNA evidence in unsolved cases. • Case to case hits: Combine investigation • Case to offender hits: Case potentially solved • 171 labs in 48 states. • NDIS: FBI National DNA Bank • SDIS: State DNA Databank • LDIS: Local DNA Databank OJ Simpson - June 1994 • Nicole Brown Simpson & Ron Goldman found brutally murdered in OJ’s house (CA). • Flagship case for Forensic DNA (after it passed Frye hearings, it was established as accepted science).