Primer Design

Primers can be designed directly against the sequences annotated in CnidoSite, or against a sequence you paste in. Design is performed by primer3 (version 2.6.1) running on this server — your sequence is not sent to any third-party website. For reference, the primers released with this database were designed with an optimal melting temperature of 60°C (58–62 °C), an optimal primer length of 20 bp (18–24 bp), and a GC content between 40% and 60%, with self-complementarity restricted to limit primer-dimer formation; that parameter set is the CnidoSite published protocol preset below.

Template taken from CnidoSite: EVM0014385.1 (EVM0014385.1), 1,080 bp.
Template

Two ways to supply a template: pick a species and a gene / transcript ID, or paste your own sequence. If the gene ID is found it is used; the pasted sequence is used otherwise. A template must be at least 30 bp.

Load example sequence
Primer parameters
Advanced parameters (any field left empty keeps the preset value)

A value that is not a number is ignored. The product size range is applied only when both of its fields are filled in and the maximum is at least the minimum.

Melting temperature
Primer length and GC content
Product and output
Self-complementarity and probe
Download TSV
Design results sorted by primer3 penalty, lowest first

Template 1,080 bp · parameter preset CnidoSite published protocol (Tm 60 [58-62] °C, 20 [18-24] bp, GC 40-60%) · 5 primer pairs returned.

Pair Left primer (5'→3') Position Len Tm (°C) GC (%) Right primer (5'→3') Position Len Tm (°C) GC (%) Product (bp) Penalty
1 GGGAGAACATTGCGAAACCG 129–148 20 59.832 55.000 GCAAGGCGGATTGCATTCAT 331–350 20 59.896 50.000 222 0.272
2 GCGAAACCGAACTTTGCCAA 140–159 20 60.249 50.000 GCAAGGCGGATTGCATTCAT 331–350 20 59.896 50.000 211 0.352
3 TTGCGAAACCGAACTTTGCC 138–157 20 60.249 50.000 GCAAGGCGGATTGCATTCAT 331–350 20 59.896 50.000 213 0.352
4 AAGTGACCCATGGATCTGGC 77–96 20 59.743 55.000 GCAAGGCGGATTGCATTCAT 331–350 20 59.896 50.000 274 0.361
5 GCACGTGCAAGCAGCTAAAA 3–22 20 60.318 50.000 CGGTTTCGCAATGTTCTCCC 129–148 20 59.832 55.000 146 0.486
Primer map pair 1 (lowest penalty) · product 222 bp at template position 129–350 · the two tracks are drawn at different scales

Left primer — binds the template strand as listed (5′→3′)Right primer — its reverse complement binds hereProduct

Template1,080 bpproduct 222 bp · template 129–350product 222 bpleft primer, template 129–148right primer anneals here, template 331–35012715418101,080Amplicon222 bpleft primer GGGAGAACATTGCGAAACCG · 5′→3′right primer GCAAGGCGGATTGCATTCAT · its reverse complement binds the template strandinterior 182 bp129184240295350
Left primer
GGGAGAACATTGCGAAACCG
template 129–148 · 20 bp · Tm 59.832 °C · GC 55.000 %
Right primer
GCAAGGCGGATTGCATTCAT
template 331–350 · 20 bp · Tm 59.896 °C · GC 50.000 %

Amplicon sequence (5′→3′ on the template strand, 222 bp) — blue is the left primer, red is where the right primer anneals. Copy from here to order or to check a base by eye.

GGGAGAACATTGCGAAACCGAACTTTGCCAATTCGATTCTGATAGATTATATCTCGATACATTTGAAAATCCCTATTGTCCAGATGTAGGATGTTCTGAAGAGGAGAAGAAGAAATGTCAACACGGATTTGTTCAAAATTTGTGTCTTTTCATCATTGCATTTGCGCCAATAATAGGACCTATTCTGGTAGATATTGCCAATATGAATGCAATCCGCCTTGC

The right primer is listed as its own 5'→3' sequence; what anneals to the template strand shown here is its reverse complement, so the highlighted stretch is complementary to the listed sequence. That is expected.

How to read this table. Position is a 1-based interval on the template, and both primers use the same convention: it is the stretch the primer occupies on the template strand (for the left primer, starting at its 5’ end; for the right primer, the region it anneals to, i.e. where the reverse complement of the listed sequence sits on the template). The two coordinates in a row can therefore be subtracted directly, and the amplicon view above marks both of them so you can check them by eye. Penalty is primer3’s weighted sum of the deviations from your constraints — lower is better, and the pairs are returned in that order. Tm is computed by primer3 from the SantaLucia thermodynamic parameters at the salt and primer concentrations in effect. The primer sequences themselves are 5’→3′ and can be ordered as they stand; the right primer anneals to the template as its reverse complement.

Specificity has not been assessed. This page only designs primers; it does not check whether they also anneal elsewhere in the genome or transcriptome. Once you have candidates, confirm each primer sequence with this site’s BLAST. The Tm and GC settings above are the design targets, and the annealing temperature still has to be optimised at the bench.

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