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What is the procedure for admitting scientific evidence in court?
- Admissibility hearing should be held by trial court
- Ruling has to be confirmed by appellate court
- Supreme court approves the ruling
- Then legal precedent for admissibility is established
What confounds the acceptance of scientific evidence?
- Three admissibility standards
- Federal rules of Evidence
- The Daubert Standard
When was the first time DNA was used in a criminal trial in the USA?
What were the challenges to PCR based DNA testing?
- Specific application of the methodology
- Disclosure of development validation and proprietary reagents
What is certification?
Refers to qualification of individuals working in the forensics lab
What is the purpose of accredidation?
To improve the quality of Forensic Crime Laboratory Services
What is Forensic Science (forensics)?
The application of a broad spectrum of sciences to answer questions of interest to the legal system
What are some real world DNA fingerprinting applications?
- Crime Scene
- Family Pedigree
- Anthropology Studies
- Food Identification
- Human Remains Identity
- Monitoring Transplants
What are the 6 basic concepts in physical evidence?
- The division of matter
- Classification or Individualization
What are the 2 fundamental scientific principles for analysis of forensic evidence?
- Divisible matter- prior event before transfer
- Transfer matter- sharing or exchanging of matter when crime is commited
What is identification?
Answers what it is (type of collected evidence)
What is classification?
Categorizing of collected evidence
What is individualization?
How much DNA is used for forensics?
What is genetics?
The study of gene variation and inheritance
What are alleles?
An alternative form of a gene or a trait or marker
What is a locus?
- The site where a molecule of a gene
- A DNA sequence resides on the chromosomes
What is a genetic marker frequency?
The frequency of a given marker in a population
What is genetic concordance?
The measure of strength of marker evidence
What does linkage disequilibrium explain?
Non-random association of alleles at two or more loci
How is in vitro DNA replicated?
What is HLA-DQ alpha, HLA-DQA1 and how are the results shown?
- Human leukocyte antigen locus
- Marker found in human chromosome 6
- Shown in strip reverse dot blot
What is AmpliType PM-DQA1 (polymarker)?
- Modified system of HLA-DQA1
- Uses polymarkers to increase the power of discrimination (using PCR)
What are the sources of DNA in human cells?
- Nuclear DNA
- Mitochondrial DNA (autonomous circle of DNA)
- mtDNA (inherited from maternal side only)
What is hetroplasmy?
A mixture of mtDNA type
What are samples for mtDNA?
What is the advantage of multiplex PCR?
10 or more STR loci can be simultaneously amplified
What are the 4 DNA isolation techniques?
What is DNA isolation?
A technique used to extract and separate DNA only from other cell components and foreign materials
What is Chelex Extraction used for and how does it work?
- Very Small Samples
- Uses chemical beads, chelex, that collect and bind all non-DNA materials
- Not good for RFLP
What is QiaAmp Extraction?
- Silica columns bases method
- Cell/nucleus lysed and rinsed
What is organic extraction?
Need larger sample, but maintain quality and quantity better
What is differential extraction?
A technique to isolate DNA from other cell samples mixed with sperm cells
What is reverse dot blot PCR?
Probes are immobilized on a strip and PCR samples are added to the strip
What are the 3 steps of PCR?
What is the marker specific to male DNA?
What things can degrade DNA?
- UV light
What is star activity?
Non stringent conditions for performance of specific enzyme
What is stochastic fluctuation?
Unequal representative of alleles due to sampling errors
What is preferential amplification?
- One allele is amplified more than the other (looks homozygous)
- Allelic dropout
What is the purpose of DNA typing?
To identify if a person is the source of biological evidence
What are the two typing systems for profiling?
- Detecting continuous alleles (RFLP)
- Detecting discrete alleles (PCR)
What are the 3 ways samples show genetic concordance?
- Samples are from the same source
- Coincidence (2 people have the same genetic profile for a particular marker)
- Error in collection of handing of a sample
What two genetic models do we used to estimate allele frequency?
- Hardy-Weinberg Equilibrium
- Linkage Equilibrium
What does the frequency estimate?
- The evidence profile, not the suspect profile
- The evidence profile is then matched
What are the steps used in estimating profile frequency?
- Population studies (collect data)
- Frequency is tested for departure from HW and LE
- Calculate Genotype frequency
- Calculate frequency by multiplication of loci
Why is it necessary to establish the DNA databank?
What is the difference between a databank and a database?
- bank- all information about the offender and process of handling the case
- base- part of the databank
What is required for successful Databank?
- Sample collection
- Sample analysis
- Establishing a database for analyzed data