Last updated: April 21, 2026

How to Check Oligo Pool Design Rules Before Ordering

Q: What is the ideal GC content for oligo pools?

40-60% is ideal for synthesis efficiency and uniform amplification. Range 30-70% is acceptable. Below 25% or above 75% causes synthesis failures, poor representation, and PCR bias. Use our GC Content Analyzer to screen all sequences.

Q: How do I handle oligos with extreme GC content?

For GC-rich regions (>70%): add GC-poor flanking sequences, use 7-deaza-dGTP in amplification, or substitute inosine. For AT-rich regions (<30%): shorten the oligo if possible, or add GC-rich adapter sequences to normalize Tm.

Q: What secondary structure strength causes synthesis problems?

Hairpins with ΔG < -3 kcal/mol at 60°C should be flagged. Below -5 kcal/mol, expect significant synthesis dropout. Redesign by introducing silent mutations, shifting the sequence window, or breaking the stem with mismatches.

Q: Should all oligos in a pool be the same length?

Within ±10% of target length is ideal. Up to ±15% is acceptable for most applications. Large length variation causes PCR amplification bias (shorter oligos amplify faster). Add padding sequences if needed to normalize lengths.

Use this page when you need to decide whether a pool is ready to send to a vendor. It covers the sequence checks that prevent rejections, dropout, amplification bias, and weak representationbefore you place an oligo pool order.

Bioinformatics representation of DNA secondary structures

Analyzing DNA hairpins and GC distribution to optimize pool synthesis.

Pre-Order Design Rules Checklist

Parameter	Optimal Range	Acceptable	Avoid	Impact	Tool
Oligo Length	80-150 bp	60-200 bp	>250 bp	Error rate, full-length yield	Check →
Length Uniformity	±5 bp	±10 bp	>±20 bp	PCR amplification bias	Check →
GC Content	40-60%	30-70%	<25% or >75%	Synthesis dropout, PCR bias	Check →
Homopolymers	≤3 nt	≤4 nt	≥5 nt (esp. poly-G)	Synthesis errors, deletions	Check →
Hairpin ΔG	> 0 kcal/mol	> -3 kcal/mol	< -5 kcal/mol	Synthesis dropout, PCR stall	Check →
Repeats	≤3 bp unit, ≤2 copies	≤4 bp unit	Long tandem repeats	Replication slippage	Check →
Tm Variation	±2°C	±5°C	>±10°C	Uneven hybridization	Check →
Poly-T Runs	≤3 consecutive T	4 T	≥5 T	Pol III termination (CRISPR)	Check →

Application-Specific Checks Before Submission

CRISPR Libraries

→Max poly-T = 3 nt (Pol III terminates at TTTT)
→Include scaffold sequence (76 bp for SpCas9)
→Avoid BsmBI/BsaI sites in spacer
→Add 5' CACCG adapter for BsmBI cloning

Design a CRISPR sgRNA pool →

NGS Capture Probes

→Normalize Tm to 65-75°C across all probes
→Tile 2x (60 bp overlap in 120 bp probes)
→Add biotin modification specification
→Avoid >80% homology to off-target regions

Design a custom NGS panel pool →

Mutagenesis Libraries

→One oligo per variant (no degenerate codons)
→Use preferred codons for target organism
→Include 25-40 bp homology arms for Gibson
→Add wild-type and synonymous controls

Design a mutagenesis pool →

Gene Assembly

→20-40 bp overlaps with Tm 62-70°C
→Remove internal restriction sites (BsaI/BsmBI)
→Add unique amplification primers per gene
→Codon-optimize for target organism

Assemble genes from a pool →

Pre-Synthesis QC Workflow

Run Batch Sequence QC

Upload all sequences. Automatically flags: GC extremes, homopolymers, repeat regions, length outliers.

Use Batch QC →

Check GC Content Distribution

Visualize GC% across all oligos. Identify clusters outside 30-70% range for redesign.

Use GC Analyzer →

Predict Secondary Structures

Screen for strong hairpins (ΔG < -3). Redesign or flag for vendor attention.

Use Structure Predictor →

Normalize Melting Temperatures

Calculate Tm for all oligos. Adjust length or add adapters to bring outliers within ±5°C of median.

Use Tm Calculator →

Frequently Asked Questions

What is the ideal GC content for oligo pools?▾

40-60% is ideal for synthesis efficiency and uniform amplification. Range 30-70% is acceptable. Below 25% or above 75% causes synthesis failures, poor representation, and PCR bias. Use our GC Content Analyzer to screen all sequences.

How do I handle oligos with extreme GC content?▾

For GC-rich regions (>70%): add GC-poor flanking sequences, use 7-deaza-dGTP in amplification, or substitute inosine. For AT-rich regions (<30%): shorten the oligo if possible, or add GC-rich adapter sequences to normalize Tm.

What secondary structure strength causes synthesis problems?▾

Hairpins with ΔG < -3 kcal/mol at 60°C should be flagged. Below -5 kcal/mol, expect significant synthesis dropout. Redesign by introducing silent mutations, shifting the sequence window, or breaking the stem with mismatches.

Should all oligos in a pool be the same length?▾

Within ±10% of target length is ideal. Up to ±15% is acceptable for most applications. Large length variation causes PCR amplification bias (shorter oligos amplify faster). Add padding sequences if needed to normalize lengths.

How to Check Oligo Pool Design Rules Before Ordering

Pre-Order Design Rules Checklist

Application-Specific Checks Before Submission

CRISPR Libraries

NGS Capture Probes

Mutagenesis Libraries

Gene Assembly

Pre-Synthesis QC Workflow

Run Batch Sequence QC

Check GC Content Distribution

Predict Secondary Structures

Normalize Melting Temperatures

Frequently Asked Questions

Next Pages to Open

Design an Oligo Pool Before Ordering

Read Oligo Pool QC Metrics

Troubleshoot Oligo Pool Problems

Choose Between Array and Column Synthesis

Order an Oligo Pool

Run Batch QC Before Ordering