CGL Sample Preparation and Handling 2 — Questions and Answers
Question 1: When collecting a buccal swab DNA sample for genealogical testing, how long should the donor refrain from eating, drinking, or smoking beforehand?
- 15 minutes
- 30 minutes (Correct answer)
- 60 minutes
- No restriction is necessary
Correct answer: 30 minutes
Donors should refrain from eating, drinking, or smoking for at least 30 minutes before providing a buccal swab to avoid contamination of the sample.
Question 2: Which environmental factor poses the greatest risk to the long-term integrity of a stored DNA sample?
- Low humidity
- Exposure to heat and UV light (Correct answer)
- Low atmospheric pressure
- Proximity to magnetic fields
Correct answer: Exposure to heat and UV light
Heat and UV light cause DNA strand breaks and accelerate degradation, making them the primary environmental threats to stored samples.
Question 3: A genealogist discovers that a donor's saliva sample tube shows a broken seal upon arrival at the lab. What is the correct course of action?
- Process the sample immediately to minimize further exposure
- Refrigerate it and process within 24 hours
- Reject the sample and request a new collection (Correct answer)
- Add a preservative solution and proceed
Correct answer: Reject the sample and request a new collection
A compromised seal indicates potential contamination or degradation, so the sample must be rejected and a new one collected to ensure result validity.
Question 4: When preparing archival paper documents for digitization in a genealogical project, which glove material is preferred to avoid damage?
- Latex gloves
- Vinyl gloves
- Nitrile or cotton gloves (Correct answer)
- No gloves are recommended for delicate papers
Correct answer: Nitrile or cotton gloves
Nitrile or cotton gloves prevent oils and acids from skin from transferring to paper, while latex can leave residues; bare hands are not recommended.
Question 5: Which of the following DNA sample types is most suitable for situations where a cheek swab cannot be obtained from an elderly or infirm individual?
- Hair with the root attached (Correct answer)
- Clipped fingernails
- A strand of hair without the root
- Saliva collected on filter paper
Correct answer: Hair with the root attached
Hair with the root still attached contains nuclear DNA suitable for genealogical testing, unlike rootless hair which only has mitochondrial DNA.
Question 6: In genealogical DNA testing, what does 'chain of custody' documentation primarily protect against?
- Sample degradation during shipping
- Allegations of sample substitution or tampering (Correct answer)
- Errors in the laboratory extraction process
- Misidentification of haplogroups
Correct answer: Allegations of sample substitution or tampering
Chain of custody documentation creates a verifiable record of who handled the sample at each step, protecting against claims of substitution or tampering.
Question 7: Which storage temperature is generally recommended for long-term preservation of DNA samples in a biobank or genealogical archive?
- -20°C (standard freezer)
- -80°C (ultra-low freezer) (Correct answer)
- 4°C (refrigerator)
- Room temperature with desiccant
Correct answer: -80°C (ultra-low freezer)
Ultra-low freezer storage at -80°C best preserves DNA integrity over decades by virtually stopping enzymatic degradation.
CGL Sample Preparation and Handling 2
When collecting a buccal swab DNA sample for genealogical testing, how long should the donor refrain from eating, drinking, or smoking beforehand?