Interpretation Flashcards
What is the difference between limited and complex?
Limited = “less” information present; <18 loci without the possibility of dropout, profiles in stochastic range with allelic activity below analytical threshold indicating additional contributor(s) may be present, profiles with peak heights at multiple locations indicating additional contributor(s) may be present).
Complex = “more” information present; more than two contributors, the potential biological relationship prohibits the determination of the number of contributors, a combination of human and non-specific amplification prohibiting interpretation of the profile.
List the three different thresholds that we have.
- Analytical threshold
- Stochastic threshold
- Saturation threshold
Define the analytical threshold and what is the value?
This defines the height requirement at and above which detected peaks can be reliably distinguished from background noise (100rfu).
Define the stochastic threshold and what is the value?
It is the peak height or signal magnitude below which it is reasonable to assume that allelic dropout of a sister allele in a heterozygous pair may have occurred (350rfu).
Define the saturation threshold and what is the value?
It is an upper RFU threshold which should only be applied to a sample exhibiting high peak heights where baseline noise or pull up is present above the analytical threshold causing artifacts to be labeled as a true peak (300rfu).
List some steps that you would take when evaluating a profile to determine the number of contributors?
First, examine of the number of alleles detected at each locus. Some circumstances may also require the analyst to examine peak heights, peak height ratios, and the baseline.
Alleles detected above the analytical threshold but present at less than 7 autosomal loci is what?
Insufficient DNA
Define insufficient quant value. How many locations would be present to call a profile insufficient DNA?
A. ≥ seven autosomal loci detected and total autosomal amplification target of <125pg.
B. < seven
What is the difference between reasonable expectation and intimate?
RE: a scenario that provides feasibility for an individual’s DNA to be present on an item (e.g., steering wheel, wallet, cell phone, clothing, etc.)
Intimate: a biological sample from an evidence item that is obtained directly from an individual’s body
What three types of conclusions do we have when comparing evidence to known references?
- Inclusion
- Exclusion
- Inconclusive
What does inconclusive mean?
If after comparison to a known reference, the individual cannot be excluded or included
True or False. Once an inclusion is made, we do not have to compare any new references to the evidence.
False. Comparisons will be made between all interpretable evidence profiles and reference profiles.
What steps would you take when interpreting data?
- Evaluate the data from the electropherogram to determine if the results are interpretable or uninterpretable.
- Establish the minimum number of contributors and evaluate sex determination.
- Determine if mixture data is distinguishable or indistinguishable.
- Designate genotype(s) if applicable.
- Utilize available assumptions for further resolution of genotypes if appropriate.
- Compare to applicable references.
- Perform statistical evaluation when applicable.
What does PABT stand for and what does it indicate?
Possible allele(s) below threshold. It indicates dropout and/or additional contributors may be present below the analysis threshold.
What is the difference between distinguishable vs indistinguishable?
Distinguishable - mixtures where relative peak height ratios allow for the interpretation of the genotype of the major and/or minor contributors at ≥18 locations. Mixture ratios greater than 3:1 show better separation between contributors.
Indistinguishable - mixtures where it is not possible to distinguish individual genotypes because the amounts of DNA from the two contributors are similar (~1:1 ratio).
