DNA Analysis & Interpretation Flashcards
7 cards from real CFC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 DNA Analysis & Interpretation flashcards as text
Mitochondrial DNA (mtDNA) is particularly useful in forensic cases involving which type of evidence?
Answer: Hair shafts without roots, bones, and teeth
mtDNA is found in high copy numbers per cell, making it ideal for analyzing highly degraded or low-template samples like rootless hairs and ancient bones.
The Combined DNA Index System (CODIS) database uses which core set of STR loci for forensic DNA profiling in the United States?
Answer: 13 core loci established in 1997, expanded to 20 core loci in 2017
CODIS originally used 13 core STR loci; the FBI expanded the core to 20 loci effective January 2017 to reduce adventitious hits and increase discriminating power.
In interpreting a DNA mixture, a forensic analyst determines that a suspect cannot be excluded. What additional information is essential to include in the report?
Answer: A statistical weight such as combined probability of inclusion or likelihood ratio
A cannot-exclude conclusion alone is insufficient; a statistical weight must accompany it to convey the significance of the non-exclusion.
Which type of DNA testing is most appropriate for determining the maternal lineage of skeletal remains when nuclear DNA is too degraded?
Answer: Mitochondrial DNA HVI/HVII sequencing
Mitochondrial DNA is maternally inherited and present in high copy numbers, making mtDNA sequencing ideal for degraded samples and maternal lineage tracing.
A DNA profile from evidence shows alleles at 18 of 20 CODIS loci matching a suspect. The two missing loci show no data. How should the examiner interpret this?
Answer: The profile is a match with a partial profile; statistical weight must reflect the tested loci only
Comparisons are valid for tested loci, but statistics must be calculated only on loci with results, and the partial nature must be disclosed.
What is 'touch DNA' and what challenge does it present in forensic casework?
Answer: DNA from epithelial cells deposited by skin contact; challenges include very low template amounts and transfer/secondary transfer issues
Touch DNA consists of skin cells left by handling objects; the very low quantities and risk of secondary transfer make interpretation and attribution challenging.
A forensic examiner is asked to interpret a DNA result where the evidence profile has more than two alleles at multiple loci. What does this indicate?
Answer: The presence of a DNA mixture from multiple contributors
More than two alleles at multiple loci is the defining indicator that the sample contains DNA from more than one individual.