FDC Forensic Laboratory Procedures 3

Question 1

Which safety class of biological hazard does most human blood evidence fall under in a forensic DNA laboratory?

Accepted Answer

BSL-2

Answer

Human blood is classified as a BSL-2 hazard because it may contain bloodborne pathogens such as HIV and hepatitis B/C.

Question 2

What is the primary reason forensic DNA laboratories use positive displacement pipettes for highly viscous or volatile samples?

Accepted Answer

To reduce aerosol contamination compared to standard pipettes

Answer

Positive displacement pipettes use a disposable piston that contacts the liquid directly, eliminating aerosols that could contaminate samples or expose analysts to hazardous substances.

Question 3

When performing differential extraction for sexual assault evidence, what is the purpose of the first centrifugation step?

Accepted Answer

To pellet sperm cells separately from epithelial cells

Answer

The first centrifugation pellets all cellular material; differential lysis then lyses epithelial cells first, and a second centrifugation separates the sperm cell fraction from the epithelial cell lysate.

Question 4

A DNA quantification result shows an OD260/OD280 ratio of 1.4. What does this indicate about the sample?

Accepted Answer

The sample likely contains protein contamination

Answer

A 260/280 ratio significantly below 1.8 indicates protein contamination, because proteins absorb strongly at 280 nm.

Question 5

Which of the following best describes a NIST SRM (Standard Reference Material) used in forensic DNA analysis?

Accepted Answer

A characterized reference material with certified property values used for assay validation

Answer

NIST SRMs are certified reference materials with well-characterized genetic profiles used to verify assay performance and ensure measurement accuracy.

(FDC) Forensic DNA Certification Practice Test

(FDC) Forensic DNA Certification Practice Test

FDC Forensic Laboratory Procedures 3