STEP ONE: DNA EXTRACTION

• Before a DNA profile can be prepared from a human sample, the DNA must be isolated from other organic and non-organic components of the sample. The type of sample will determine the particular isolation technique used.
• Lab Technicians extract DNA from the nucleus of cells found in DNA samples such as human tissue, hair, bone,  blood or fluids.
• The sample is "washed" with chemicals, removing unwanted cellular material.
• Isolation takes about one to four hours depending on sample type . 
• Once the DNA has been extracted from the sample, a number of different techniques can be used to develop a DNA profile.

STEP TWO: DNA QUANTITATION

• Tests are run to determine the amount of DNA present in the sample.
• Estimates are made by comparing the sample to standards of known quantities of DNA.
• The targeted amount is approximately 1 nanogram (billionth of a gram).
• DNA Quantitation takes up to two hours.
• If inadequate quantities of DNA are recovered, the first step may be repeated. 
• DNA Samples are quantitated for the following reasons: 
  • improved amplification efficiency
  • fewer off-scale or over-amplified samples 
  • balanced profiles
  • absence of artifacts
  • reliable data interpretation
  • reduced need for re-analysis 
  • cost effectiveness 
  • conservation of sample 

STEP THREE: PCR AMPLIFICATION of MULTIPLE STR MARKERS

• Chemicals are added to the sample to allow specific fragments of DNA to reproduce millions of times.
• 13 DNA locations are targeted for examination in a device that cycles about 28-32 heating and cooling steps.
• Polymerase Chain Reaction (PCR) takes approximately three hours.

STEP FOUR:  GENOTYPING

• PCR Products are separated and detected.
• A genetic analyser records images of DNA segments as it moves through a small tube.
• Results appear as spikes or peaks similar to an EKG chart.
• A computer generates a picture of data represented as numbers as compared to standards.
• The numbers correlate to one of the 13 specific locations labeled in the PCR step - that is a person's DNA profile.
• Typing may take 20 minutes per sample.

STEP FIVE:  COMPARISON OF RESULTS

• A DNA Expert reviews the DNA profile produced during Genotyping to determine if there is a match by comparing it t other sample results.
• A match would indicate DNA was contributed by a particular individual.
• A non-match would indicate an individual is excluded as the donor.
• Interpretation may take less than an hour but is dependent on the quality of the sample being tested.
• Statistical weight may be given to the profile by calculations from a population database.
• Generation of Case report with Probability of Random Match.