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9 Cards in this Set
- Front
- Back
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Basic Principles of Forensic Identification |
1. Each of us is genetically unique 2. If enough variation is tested, each of us can be uniquely identified 3. DNA is found in nearly all cells (Blood, semen, hair) 4. DNA from evidentiary samples can be matched to implicate or exonerate 5. Same principles are applied in paternity |
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Short Tandem Repeats |
Used in Forensic Analysis. Each of us have varying lengths of these noncoding repeats that differ between individuals. Homozygote= Both alleles are same length Heterozygote= Alleles differ and can be resolved from one another |
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PCR |
Denature Anneal Elongate Repeat 20 cycles generates 1,000,000 fold increase in amount of DNA. Increases signal to noise ratio |
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Gel Electrophoresis |
DNA fragments separated and move based on size. DNA migrates toward positive electrode because its backbone is negatively charged. Larger peices migrate slower, smaller pieces migrate quickly. Use DNA/RNA/Protein ladder in order to give a rough estimate of fragment size |
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Calculation of Random Match Probability using the Multiplication Rule |
1. Assuming independence of each marker, the total random match is the probability given by multiplying the individual frequencies of each gene together. |
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Paternity Analysis |
Multiply Gene (Allele) Frequencies together because we already know the mothers complement of DNA to the offspring. Multiply gene frequencies to assess the chance that another male in the general population contributed the observed alleles to the baby. |
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Potential Issues in Analysis |
1. Was DNA sample collected, processed, and analyzed properly? Chain of custody, contamination, or data analysis? 2. Reference population appropriate? 3. Is expert whitness really an expert? |
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Current Analysis |
1. DNA accepted as evidence in court 2. CODIS database contains STR profiles of more than 13 million americans (12 million convicted offenders) 3. DNA evidence use is increasingly standard and common |
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Whats new? |
1. Estimating ethnicity of contributor using DNA sample 2. Prediction of observable characteristics 3. Rapid DNA typing at the crime scene (using lab on a chip and microfluidics) |
