ANTH 2220 – Positive ID & Forensic DNA & Forensic Odontology
ANTH 2220 – Positive ID & Forensic DNA & Forensic Odontology ANTH 2220-01
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This 4 page Class Notes was uploaded by Jazmine Beckstrand on Saturday September 17, 2016. The Class Notes belongs to ANTH 2220-01 at University of Utah taught by Derinna Kopp in Fall 2016. Since its upload, it has received 6 views.
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Date Created: 09/17/16
ANTH 2220 – Positive ID & Forensic DNA & Forensic Odontology Definitions Key Concepts Locations * = on exam Deoxyribonucleic acid (DNA): the fundamental "blueprint" of all living matter, the genetic information that dictates the form and development of an organism. Arranged as a double helix Each strand of helix consists of long chains of nucleotides Nucleotides: composed of a phosphate group (a type of sugar), and one of the four nitrogen bases Nitrogen bases - adenine (A), thymine (T), guanine (G), and cytosine (C) Genes: provide particular genetic information for an organism (i.e. eye color, height, hair texture, skin color, etc.) Most genes are made up of 5-10,000 base pairs (AT or CG pairs) Genome: one cell's collection of chromosomes. Humans inherit a genome of 23 chromosomes per parent. DNA Typing: describes the system of assessing variation in sections of DNA for analysis. Refers to a variety of methods which isolate and extract sections of DNA for observation and comparison. Current typing system is short tandem repeats (STR) STRs are DNA regions with repeat units 2-6 bp in length Repeated a variable number of times; highly variable among individuals Each STR is "tagged" using a fluorescently labeled primer Often amplified in a multiplex reactions; one PRC reaction can amplify more than one allele STR products are then separated by size for analysis DNA Fingerprinting: original method; looks at sections of DNA located in different regions on different chromosomes. "multi-locus" typing system. Produces patterns that are entirely unique to an individual except in identical twins. Results are usually rendered as a sequence resembling a bar code. DNA Profiling: looks at one area on a specific chromosome. Most recent development Produces patterns that unrelated people are most unlikely to share. Traits are not entirely unique in a population, so they are not considered fingerprints. Role of Forensic Odontology Mass disasters Bite mark evidence Child abuse Civil litigation Person injury, malpractice, dental fraud Reasons for Establishing Identity Settlement of insurance claims Settlement of the individual's estate Social Security benefits Allowance of surviving spouse to remarry Establishment of a corpus delicti in criminal matters Burial of remains in keeping with religious beliefs What makes dental identification work? Dental outlasts all other body tissues Dental restorations and prostheses are extremely resistant Radiographs can provide objective data Infinite number of combinations Comparison antemortem and postmortem records for identification Antemortem records - relatives, hospitals or other health care facilities, dental schools, healthcare providers, employer dental insurance carrier, public aid insurance administrator Postmortem record - comprehensive charting, x-rays, photographs, dental impressions, time lapse Making Postmortem Records Teeth present Erupted vs. unerupted/impacted Missing teeth Congenitally missing, lost antemortem, lost perimortem, lost postmortem Pulp chamber and root canal morphology Root canal therapy (gutta percha, silver points, endopaste) and retrofill procedures Apicoectomy Internal resorption Dental restorations Metallic restorations (amalgams, gold or non-precious metal crowns/inlays, endoposts, pins, fixed prostheses, implants) Non-metallic restorations: acrylics, silicates, composites, porcelain, etc. Partial and full removal prostheses Dental Identification Conclusions Positive Identification: The antemortem and postmortem data match in sufficient detail, with no unexplainable discrepancies, to establish that they are from the same individual. Possible Identification: the antemortem and postmortem data have consistent features but, because of the quality of either the postmortem remains or the ante-mortem evidence, it is not possible to establish identity positively. Insufficient Evidence: The available information is insufficient to form the basis for a conclusion. Exclusion: the antemortem and post-mortem data are clearly inconsistent. Forensic DNA - use of genetic information to match biological evidence with victim/offender Two Types of DNA Nuclear (chromosomal) mtDNA (mitochondrial) 100% inherited from mothers Circular morphology Hundreds to thousands of copies per cell Easier to extract from degraded samples Notes: humans share over 99% of DNA, only about 0.3% is unique (not conserved) 0.3% = 1 million differences in nitrogen base pair patterns DNA is found in all body cells (expect mature red blood cells) We leave a little bit of DNA everywhere we go Most forensic sources of DNA are bodily fluid or transferred cells DNA Polymorphism: "many forms"; regions of DNA differ from person to person. Locus: site of location on a chromosome; plural = loci. Allele: different variants which can exist at a locus. DNA Profile: the combination of alleles for an individual. DNA Extraction For each biological source of DNA you need a chemical purification method to separate DNA from everything else. The amount of time and complexity of these methods depends on both the quantity and quality of the source. Purified DNA Once DNA has been purified you can analyze it with two methods Restriction Fragment Length Polymorphism (RFLP): using DNA "cutters" to separate DNA into fragments - DNA fingerprinting Amplification or PCR: (Polymerase Chain Reaction) a technique for "replicating" DNA in the laboratory region to be amplified defined by PRIMERS Electrophoresis: a technique for separating molecules according to their size. CODIS: Combined DNA Index System Instituted in 1994 by the FBI Made up of two indices: Convicted offender index (DNA from convicted felons) Forensic case Index (DNA from crime scenes) Based on 14 STR loci Probability of 2 unrelated individuals matching at all 13 sites = 1 trillion Note: it is easier to exclude a suspect than to convict someone based on a DNA match. The FBI estimates that 1/3 of initial rape suspects are excluded because DNA samples failed to match. It is important to examine all other clues, aside from DNA DNA Limitations Not always preserved Can't speak to perimortem trauma or postmortem alterations Can build a genetic profile, but not a biological profile (age, sex, ancestry, etc.) A genetic profile depends on comparative samples to match genetic identity
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