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gBlocks Gene Fragments

Pure confidence

gBlocks™ Gene Fragments are double-stranded DNA fragments of 125–3000 bp in length. They are the industry standard for double-stranded gene fragments, designed for affordable and easy gene construction or modification, applications such as antibody research and CRISPR-mediated genome editing, qPCR standards, and more.

NEW gBlocks HiFi Gene Fragments (1000–3000 bp in length) are optimized for the assembly of large constructs. Pick fewer colonies and drive your projects to completion faster with these high purity fragments.

  • High fidelity and purity for gene assembly
  • Compatible with all downstream cloning methods
  • Ready to use with no extra sequences to remove


gBlocks Gene Fragments in tubes

A, T, C, and G residues only. Delivered dry and normalized to 250, 500, or 1000 ng, depending on length.

gBlocks Gene Fragments in plates

Orders require a minimum of 24 fragments per plate. Resuspended in 25 μL of nuclease-free water (concentration: 10 ng/μL). Shipped on dry ice within 10 business days of order confirmation (excluding Fridays).


gBlocks HiFi Gene Fragments in tubes

There are no order minimums for tubes. Shipped dry within 6–10 business days of order confirmation (excluding Fridays).

gBlocks Gene Fragment Libraries in tubes

Delivered dry, normalized to 200 ng. Libraries are not available in plate format.

1BD, business days. Shipping time is dependent on length and complexity of the gBlocks fragments ordered. In a few cases, shipping time may exceed the estimated time.

gBlocks Gene Fragments

gBlocks Gene Fragments are double-stranded DNA fragments 125–3000 bp in length with a median error rate of less than 1:5000. They are manufactured with the same industry-leading, high-fidelity synthesis chemistries that were developed for our Ultramer™ DNA Oligos.

Each gBlocks Gene Fragment goes through a quality control process, which includes size verification by capillary electrophoresis and sequence identification by mass spectrometry. This rigorous testing ensures that most recombinant colonies obtained from cloning each gBlocks Gene Fragment will contain the desired insert. More complex sequences may need the end user to sequence additional clones.

NEW gBlocks HiFi Gene Fragments

gBlocks HiFi Gene Fragments are double-stranded DNA fragments with sizes between 1000–3000 bp and verified with a median error rate of less than 1:12,000 via NGS. These high-quality, high-fidelity constructs facilitate the assembly of large and complex sequences, matching both the length and accuracy needed to minimize the introduction of unwanted substitution or deletion errors.

With either gBlocks or gBlocks HiFi Gene Fragments, you can easily assemble and clone your DNA fragment into the vector of your choice using a variety of cloning methods, including the Gibson Assembly® method (Synthetic Genomics, Inc.) and blunt- or cohesive-end cloning protocols. For added flexibility, you can order gBlocks Gene Fragments with or without a 5′-phosphate group.

gBlocks Gene Fragment Libraries

gBlocks Gene Fragment Libraries are pooled gBlocks fragments of 251 to 500 bp in total length. gBlocks Gene Fragment Libraries are ideal for generating recombinant antibodies or for protein engineering, allowing researchers to generate hundreds of thousands of constructs within a reasonable budget. The variable regions can be up to 18 consecutive N or K bases long and must be at least 125 bp from either end of the gene fragment (Figure 1).

Figure 1. Ordering format for gBlocks Gene Fragment Libraries. Placing a K mixed base in the third position of codons eliminates the TAA and TGA stop codons from being included in the gene fragments libraries, leaving only TAG as the possible stop codon.

For gBlocks Gene Fragment Libraries, each constant region is verified similarly to standard gBlocks Gene Fragments. The final library product is size-verified by capillary electrophoresis.

High fidelity and purity for gene assembly

Both gBlocks and gBlocks HiFi Gene Fragments demonstrate consistent high sequence fidelity and purity across various lengths (Figures 2 and 3).

IDT gene fragments are compatible with all cloning methods that require double-stranded DNA as a starting material, allowing easy assembly of your desired construct sequence into your favorite cloning system. Compatible cloning systems include but are not limited to traditional cloning, Gibson Assembly® (Synthetic Genomics), Golden Gate, Gateway® (Thermo Fisher), TOPO® (Thermo Fisher), TA, and blunt-end cloning.

Figure 2. The effect of error rate on predicted cloning success. With an industry leading error rate of up to 1:12,000 for gBlocks HiFi Gene Fragments, IDT Gene Fragments demonstrate a high probability of first-time cloning success. Compared with alternate suppliers, gBlocks fragments and gBlocks HiFi fragments are up to 45% more likely to give a correct clone the first time when cloning fragments up to 3000 bps.

Figure 3. Demonstrated cloning efficiency. Based on NGS sequencing of over 500 clones, gBlocks HiFi Gene Fragments (1000–3000 bp) and gBlocks Gene Fragments (125–3000 bp) exhibited a high degree of cloning success. Compared to an alternate provider, gBlocks fragments and gBlocks HiFi fragments showed a significant improvement in cloning efficiency leading to a reduction in the time and cost to find a correct clone.

Minimal screening effort needed to find your correct clone

Using IDT gene fragments can reduce the time and expense of screening colonies compared to fragments from other suppliers (Table 1). Cloning efficiency is affected by many factors, including the cloning method used, the stability of the cell line and plasmid, vector preparation, and toxicity or stress from expression of coding sequences. The values in Table 1 represent typical screening numbers needed when using a seamless assembly method, such as Gibson Assembly or NEBuilder® HiFi assembly (New England BioLabs), and when issues mentioned above are not significant contributors to error or selection.

Table 1. Minimal screening effort is needed with gBlocks and gBlocks HiFi Gene Fragments to find a correct colony.

Length (bp)gBlocks Gene FragmentsgBlocks HiFi Gene FragmentsOther supplier
≤1000 2–3N/A5


Frequently asked questions

Sequence Information is secure and confidential at IDT. Please see our Confidentiality Statement for more information. All online ordering steps, including sequence entry and your choice of parameters, are also secure and protected.

We screen the sequence of every gene fragment order we receive to (1) identify any regulated and other potentially dangerous pathogen sequences, and (2) verify that IDT’s gene customers are legitimate scientists engaged in beneficial research.

IDT is among the five founding members of the International Gene Synthesis Consortium (IGSC) and helped to create the IGSC’s Harmonized Screening Protocol. The Harmonized Screening Protocol describes the gene sequence and customer screening practices that IGSC member companies employ to prevent the misuse of synthetic genes. IDT takes the steps set out in the Harmonized Screening Protocol to screen the sequences of ordered genes and the prospective customers who submit those orders.

For more information about the IGSC and the Harmonized Screening Protocol, please visit the website at


In October 2010, the United States government issued final Screening Framework Guidance for Providers of Synthetic Double-Stranded DNA, describing how commercial providers of synthetic genes should perform gene sequence and customer screening. IDT and the other IGSC member companies supported the adoption of the Screening Framework Guidance, and IDT follows that Guidance in its application of the Harmonized Screening Protocol. For more information, please see 75 FR 62820 (Oct. 13, 2010), or

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