FDC Forensic Laboratory Procedures 2

Question 1

When preparing a 1% agarose gel for DNA electrophoresis, what is the correct order of steps?

Accepted Answer

Dissolve agarose in buffer, cool, add ethidium bromide, pour

Answer

Agarose is dissolved in electrophoresis buffer by heating, cooled to ~60°C, then ethidium bromide or other dye is added before pouring into the mold.

Question 2

A forensic analyst receives a blood stain on fabric. What is the recommended first step in processing this evidence?

Accepted Answer

Document and photograph the stain prior to any manipulation

Answer

Documentation and photography must precede any physical manipulation to preserve the evidentiary record.

Question 3

What is the purpose of including a reagent blank in a DNA extraction batch?

Accepted Answer

To detect contamination introduced during the extraction process

Answer

A reagent blank contains all extraction reagents but no biological material, allowing detection of any contamination introduced during processing.

Question 4

Which labeling approach is required on all forensic evidence containers to maintain chain of custody?

Accepted Answer

Case number, item number, collector identity, date, and seal initials

Answer

Chain of custody requires comprehensive labeling including case number, item number, collector identity, collection date, and initials on any seal.

Question 5

During STR capillary electrophoresis, a pull-up artifact appears. What does this indicate?

Accepted Answer

Spectral overlap between dye channels causing a false peak in an adjacent channel

Answer

Pull-up (bleed-through) occurs when fluorescent dye emission bleeds into an adjacent detection channel due to imperfect spectral separation.

(FDC) Forensic DNA Certification Practice Test