Phred Quality Score
Definition
A logarithmic estimate of base-calling error probability (Phred Q = -10 log10 P). Q20 = 1% error rate; Q30 = 0.1% error rate. Developed by Brent Ewing and Phil Green (University of Washington, 1998). Forensic sequencing guidelines require Q20 minimum; Q30 is preferred across the reported window.
Related terms
- 2',3'-Dideoxynucleotide Triphosphate (ddNTP)
- A nucleotide analogue lacking the 3'-hydroxyl group present in normal dNTPs. When incorporated by DNA polymerase into a growing chain, it prevents...
- Big Dye Terminator (BDT) V3.1
- Applied Biosystems' (now Thermo Fisher Scientific's) commercial cycle sequencing kit using four spectrally distinct dichlororhodamine dyes coupled to the four ddNTPs. The...
- Cycle Sequencing
- A Sanger sequencing format using a thermostable DNA polymerase and repeated denaturation-annealing-extension cycles (typically 25-35 cycles). Produces exponentially more termination products from...
- EMPOP (ENBISI Mitochondrial Population Database)
- The ENFSI-curated reference database of forensic-grade mtDNA haplotypes used to estimate the frequency of a given control-region profile in a specified population....
- rCRS (Revised Cambridge Reference Sequence)
- The standard reference sequence for the human mitochondrial genome (NC_012920.1, 16,569 bp), used as the coordinate system for reporting all forensic mtDNA...
- Sequencing-by-Synthesis (SBS)
- The Illumina detection paradigm: reversibly fluorescent 3'-blocked nucleotides are incorporated one cycle at a time into clonally amplified clusters on a flow...
Explained in
- Sanger Sequencing Chemistry and Modern MethodsA logarithmic estimate of base-calling error probability (Phred Q = -10 log10 P). Q20 = 1% error rate; Q30 = 0.1% error rate. Developed by Brent Ewing and Phil...