Phred Quality Score (Q)
Definition
A logarithmic probability score for base-call accuracy. Q30 = 99.9% accuracy (1 in 1000 error probability). Q20 = 99% accuracy. Most forensic MPS pipelines apply a Q30 minimum threshold.
Related terms
- BAM File
- Binary Alignment/Map format, the compressed binary version of a SAM file. Stores aligned reads with their mapping positions, quality scores, and alignment...
- FASTQ
- The standard sequencing output file format containing four-line records per read: identifier, nucleotide sequence, separator, and Phred quality score string. All MPS...
- Isoallele
- Two STR alleles that share the same repeat count (and therefore appear as the same allele on CE) but differ by a...
- Stutter (MPS)
- In MPS, stutter includes both length-based stutter (as in CE, an n-1 repeat artefact from PCR slippage) and sequence-based stutter (single-nucleotide errors...
- VCF
- Variant Call Format, the standard output from variant callers (GATK, FreeBayes). Records each variant position with reference allele, alternative allele(s), genotype likelihoods,...
Explained in
- NGS Data Analysis: Allele Calling, Variant Callers and Quality FiltersA logarithmic probability score for base-call accuracy. Q30 = 99.9% accuracy (1 in 1000 error probability). Q20 = 99% accuracy. Most forensic MPS pipelines app...