PRIMER_MIN_GC=20.0 PRIMER_MAX_GC=80.0 PRIMER_GC_CLAMP=1 # At least 1 G or C in the last 5 bases PRIMER_MAX_POLY_X=4 # Max run of single base (e.g., AAAA) A major improvement in the v0.4.x lineage is the enhanced mispriming library handling.
For advanced use cases, pair Primer3 v0.4.0 with scripts (Perl, Python, or R) to parse output and iterate over multiple sequences. The input format described here remains compatible with later versions (v2.x, v3.x), making it a timeless skill for bioinformaticians. primer3 input -version 0.4.0-
PRIMER_INTERNAL_OPT_SIZE=20 PRIMER_INTERNAL_MIN_SIZE=18 PRIMER_INTERNAL_MAX_SIZE=30 PRIMER_INTERNAL_OPT_TM=65.0 # Probe Tm should be 5-8°C higher than primers PRIMER_INTERNAL_MIN_TM=63.0 PRIMER_INTERNAL_MAX_TM=68.0 Here is a real-world input for amplifying a 200 bp region from a bacterial 16S rRNA gene: PRIMER_MIN_GC=20
PRIMER_PICK_LEFT_INPUT=1 # Start of left primer search region PRIMER_PICK_RIGHT_INPUT=500 # End of right primer search region To force primers to flank a specific SNP or target: pair Primer3 v0.4.0 with scripts (Perl
PRIMER_MAX_MISPRIMING=12.0 PRIMER_MAX_END_MISPRIMING=6.0 PRIMER_NUM_RETURN=5 Running Primer3 v0.4.0 Save your input as input.txt . Then run:
PRIMER_OPT_SIZE=20 PRIMER_MIN_SIZE=18 PRIMER_MAX_SIZE=27 PRIMER_OPT_TM=60.0 PRIMER_MIN_TM=57.0 PRIMER_MAX_TM=63.0 PRIMER_MAX_DIFF_TM=3.0 Avoid 3' instability and low-complexity regions.