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gBlocks™ and gBlocks HiFi Gene Fragments

gBlocks Gene Fragments and gBlocks HiFi Gene Fragments are double-stranded DNA fragments up to 3000 bp in length, designed for affordable and easy gene construction or modification. Suited for applications such as antibody research and CRISPR-mediated genome editing, qPCR and NGS controls, and more. Drive your projects to completion faster with these high-fidelity fragments.


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

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


*Plates with less than 24 fragments will incur an additional charge at checkout.

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.
  • Up to 18 N or K mixed bases.
  • Libraries are not available in plate format.

1BD, business days. Shipping time is dependent on length and complexity of the dsDNA fragment(s) ordered. In a few cases, shipping time may exceed the estimated time.


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Product details

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.

gBlocks HiFi Gene Fragments

gBlocks HiFi Gene Fragments are double-stranded DNA fragments between 1000–3000 bp that are sequence-verified via NGS with a median error rate of less than 1:12,000. These high-quality, high-fidelity fragments 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. 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 251–500 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 (any base) or K (G or T) 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.

Product data

High fidelity and purity for gene assembly

Both gBlocks and gBlocks HiFi Gene Fragments demonstrate consistent high sequence fidelity and purity across various lengths.

Figure 2. IDT gBlocks and gBlocks HiFi Gene Fragments demonstrate high probability of cloning success. With a median error rate of 1:12,000 for gBlocks HiFi Gene Fragments, IDT Gene Fragments demonstrate a high probability of first-time cloning success. Based on data derived from NGS sequencing of gene fragments, gBlocks Gene Fragments and gBlocks HiFi Gene Fragments are up to 45% more likely to give a correct clone the first time when cloning fragments up to 3000 bps compared to an alternate supplier.

IDT gene fragment data demonstrate improved fidelity versus that from other suppliers

In a head-to-head comparison study against two other DNA synthesis suppliers, IDT’s proprietary synthesis and error correction processes resulted in gene fragments with lower error rates. Low error rates ensure more correct clones, allowing researchers to reduce the number of colonies needed to screen by as much as 50%.

Figure 3. IDT gBlocks and gBlocks HiFi Gene Fragments produce a higher percentage of correct colonies when compared to two other suppliers. Based on screening and sequencing of 24 colonies per sequence, IDT’s fragments were the only fragments to have greater than 75% correct colonies with the desired full-length sequence, and the only gene fragments to achieve greater than 90% correct colonies for fragments that were 1 kb or more in length.

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. 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 cloning method.

Table 1. gBlocks and gBlocks HiFi Gene Fragments reduce the time and expense of screening colonies. The approximate number of colonies to screen for a 90% chance of getting a correct clone.

Length (bp)gBlocks Gene FragmentsgBlocks HiFi Gene Fragments
≤1000 2–3N/A


Compatible with multiple cloning methods and workflows

IDT gene fragments are compatible with many cloning and assembly kits and automation platforms, allowing easy assembly of your desired construct sequence into your preferred cloning method. Methods include traditional cloning, Gibson Assembly® (New England Biolabs), Golden Gate, Gateway® (Invitrogen), TOPO™/TA cloning (Thermo Fisher), blunt-end cloning, and others.


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, gene fragment, and Megamer™ ssDNA 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