Forensic DNA Extraction and Analysis

Evidence assessment, sampling, DNA extraction, quantitation, amplification, separation and detection, interpretation, technical review, and reporting.

The process of releasing DNA from biological material and preparing it for subsequent analysis.

The removal of proteins, inhibitors, and other unwanted substances from a DNA-containing preparation.

An extraction method traditionally using phenol-chloroform chemistry to separate proteins and other materials from nucleic acids.

A method using a chelating resin to bind metal ions and help prepare DNA for amplification.

A method in which DNA binds to silica under suitable chemical conditions and is subsequently washed and eluted.

A purification method using particles that bind nucleic acids and can be separated from liquids using a magnetic field.

A procedure intended to separate sperm-associated DNA from other cellular DNA in suitable mixed biological samples.

No. Incomplete separation and cross-contamination between fractions can occur.

The disruption of cellular membranes or structures to release intracellular components, including DNA.

To digest proteins and help release and protect DNA during sample preparation.

To reduce disulfide bonds, including those in sperm nuclear proteins, facilitating DNA release.

A negative control processed through DNA extraction without an evidentiary sample to monitor contamination.

A reaction containing the amplification reagents without added target DNA, used to monitor contamination introduced during amplification setup.

A reaction containing known DNA expected to produce a specified amplification result.

To reduce the risk that concentrated amplified DNA contaminates unamplified evidence samples.

Unintended transfer of DNA from a previous sample or analytical process into another sample or reaction.

The unintended introduction of biological material from one sample into another.

Comparison with reference profiles from relevant personnel or others to help identify possible contamination sources.

To reduce unintended transfer of DNA and other material between samples.

The breakdown or fragmentation of DNA through chemical, biological, or environmental processes.

It can produce DNA damage that may interfere with successful amplification or interpretation.

They can promote decomposition and DNA degradation, particularly when evidence is stored improperly.

A measure comparing amplification or quantitation signals from different-sized DNA targets to help assess fragmentation.

Shorter intact fragments are more likely to remain available for amplification when DNA has been fragmented.

An STR analysis approach designed to amplify shorter DNA fragments, potentially improving results from degraded material.

The measurement or estimation of DNA amount or concentration in a sample.

To select an appropriate DNA input amount and identify potential issues such as low quantity, inhibition, or degradation.

A known amplification target included in a reaction to help assess amplification performance or inhibition.

Random variation in amplification that may produce imbalanced peaks, allele dropout, or other unpredictable profile features.

The measured fluorescence intensity of a detected peak, commonly expressed in relative fluorescence units.

Relative fluorescence units.

A laboratory-defined signal level used to distinguish reportable peaks from background noise under specified conditions.

A validated signal threshold used to assess the risk that an associated allele may have dropped out.

A difference in the heights of two allelic peaks at a heterozygous locus beyond or within expected analytical variation.

A comparison of the heights of two peaks, often used to evaluate heterozygote balance or mixture characteristics.

A spectral artifact in which fluorescence from one dye channel appears in another because of imperfect color separation.

An artifact caused by fluorescent dye-related material that may produce a broad or atypical signal.

An observed STR allele that falls outside the allele positions represented in the allelic ladder and requires appropriate evaluation.

The observation of three allelic signals at a locus, which may reflect biological variation, a mixture, or an analytical issue.

To assess the consistency of observed results and help evaluate stochastic effects or other uncertainties.

An estimate of how many individuals contributed DNA to a mixed sample.

Allele sharing, dropout, peak imbalance, low-level contributors, and artifacts can obscure the number of sources.

The statistical evaluation of genetic evidence to assess proposed biological relationships.

A likelihood ratio comparing the genetic evidence under a specified paternity proposition with an alternative proposition.

A combination of locus-specific paternity indices under appropriate genetic and statistical assumptions.

A DNA result may support who contributed biological material without establishing how or when the material was deposited.

Potential contamination affecting the extraction batch and the reliability of the associated evidence results.

DNA fragmentation may have prevented successful amplification of longer targets.

The genetic association does not independently establish the timing, mechanism, or criminal significance of the DNA transfer.