FDC DNA Analysis Techniques 4

Question 1

What is the purpose of a positive amplification control in PCR-based forensic analysis?

Accepted Answer

To verify that the PCR reagents and conditions are functioning correctly

Answer

A positive amplification control contains known DNA and confirms that PCR reagents, conditions, and the thermocycler are performing correctly.

Question 2

Which phenomenon occurs when only one allele is detected at a heterozygous locus due to preferential amplification of one allele?

Accepted Answer

Allelic dropout

Answer

Allelic dropout occurs when only one of two heterozygous alleles amplifies and is detected, often due to low template DNA or degradation affecting one allele's primer binding site.

Question 3

In next-generation sequencing (NGS) applied to forensics, what is a key advantage over capillary electrophoresis for STR typing?

Accepted Answer

Ability to resolve isoalleles and detect sequence variation within repeat units

Answer

NGS can distinguish isoalleles (alleles of the same length but different sequence) and detect sequence variation within STR repeat units, providing greater discrimination power.

Question 4

What is a 'negative reagent blank' used to detect in forensic DNA analysis?

Accepted Answer

Laboratory contamination introduced during sample processing

Answer

A negative reagent blank contains all reagents but no DNA; any DNA profile detected indicates contamination was introduced during sample processing.

Question 5

Which database does CODIS use as its core set of STR loci for national DNA profile comparison?

Accepted Answer

The expanded CODIS 20 core STR loci

Answer

CODIS expanded from 13 to 20 core STR loci in 2017, and all profiles uploaded to the national database must include these 20 loci for searching.

(FDC) Forensic DNA Certification Practice Test

(FDC) Forensic DNA Certification Practice Test

FDC DNA Analysis Techniques 4