Sequencing

11th Annual Sequencing, Finishing, and Analysis in the Future Meeting
INITIAL EVALUATION OF THE EARLY ACCESS STR
KIT V1 FOR THE ION TORRENT PGM
Wednesday, 1st June 18:30 La Fonda Mezzanine (2nd Floor) Poster (PS‐2a.01)
Kelly A Meiklejohn 1 , Sharon Wootton 2 , Joseph Chang 2 , Chien‐wei Chang 2 ,
Robert E Legace 2 , Narasimhan Rajagopalan 2 , James Robertson 1
1 FBI Laboratory, 2 Thermofisher
Forensic laboratories traditionally utilize commercial kits for STR genotyping, which simultaneously
amplify the core CODIS STR loci and tag them with fluorescent dyes for separation by capillary
electrophoresis (CE). Given the known limitations of CE typing, including the sensitivity issues
with degraded DNA and the ability to deconvolute complex mixtures, massively parallel sequencing
(MPS) is currently being evaluated as an additional tool for STR typing. In this study, we evaluated
the Early Access STR Kit v1 for the Ion Torrent PGM using both commercially available pure
native DNAs (n, 5) and forensic type DNA samples (i.e. blood, saliva and sexual fluid; n, 6). To
assess reproducibility, libraries were prepared in triplicate for each sample using 1 ng of DNA as
input (total n, 33). Initially we examined the performance of the Early Access STR Kit v1 using
the data obtained from the five commercially available pure native DNA samples based on: 1) the
depth of coverage (DoC) at each locus, and 2) the allele coverage ratio (ACR) for heterozygote loci.
The average DoC among the 25 STR loci included in the panel was quite varied, ranging from 1775
– 8219X. In all loci except D13S317 and D9S2157, the ACRs were above the acceptable value of
0.5. We only observed a few instances of discordance between the PGM genotypes and those
obtained using the traditional CE approach, indicating that reliable STR profiles can be obtained
for both pure native and forensic type DNA samples. It is likely that with further advancements and
modifications of the panel and associated analysis software prior to commercial release, instances of
discordance will be infrequent. Subsequent evaluations should be focused on assessing the ability of
the panel to detect mixtures at a range of ratios, along with the sensitivity limits.
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