gBlocks® Gene Fragments—Related DECODED Articles

Assembling gene fragments using isothermal assembly

gBlocks® Gene Fragments

gBlocks Gene Fragments are high fidelity, double-stranded DNA (dsDNA) up to 3000 bp in length that can be custom designed for virtually any cloning application, and are uniquely suited for assembling and modifying larger constructs using the Gibson Assembly™ method. gBlocks Gene Fragments provide flexibility for synthetic biology applications that is not currently available in any other product.

Gibson isothermal assembly

The Gibson isothermal assembly method is based on the technique described by Gibson et al. in Nature [1]. The method relies on the use of an enzyme mixture consisting of the mesophilic T5 exonuclease, a thermophilic ligase, and a high fidelity polymerase. Both the vector and the 5’ ends of the gBlocks fragments to be assembled are designed with 30 bp overlaps. Prior to assembly, the vector must be linearized by a separate restriction digestion or PCR amplification.

For assembly, all of the components are combined and allowed to react at 50°C, where the exonuclease begins to digest dsDNA from the 5’ ends. The exonuclease is rapidly inactivated by the high temperature, leaving complementary 3’ single-stranded DNA (ssDNA) ends that anneal. The polymerase then fills in any remaining ssDNA gaps and the ligase covalently joins the fragments together (See Figure 1 in the DECODED article, Isothermal assembly: Quick, easy gene construction).

Isothermal assembly of gBlocks Gene Fragments makes it easy to create or modify genes without the need for restriction sites in your insert or for conducting time-consuming, sequential, cloning reactions. For more information on gBlocks Gene Fragments, visit


  1. Gibson DG, Young L, et al. (2009) Enzymatic assembly of DNA molecules up to several hundred kilobases. Nature Methods, 6(5):343–345.

Product focus—custom dsDNA fragments

gBlocks® Gene Fragments

These double-stranded, sequence-verified, DNA genomic blocks, 125–3000 bp in length, designed by you, are shipped in 2–5 working days for affordable and easy gene construction or modification. They have been used in a wide range of applications including CRISPR-mediated genome editing, antibody research, codon optimization, mutagenesis, CRISPR genome editing, and aptamer expression. They can also be used for generating qPCR standards.

Learn more about gBlocks Gene Fragments at

Related articles

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Cloning Strategies Part 3: Blunt-End Cloning—Get these tips and tricks for blunt-end cloning.

Building Biological Factories for Renewable and Sustainable Products—Learn how Amyris uses genetic engineering and screening technologies to design microorganisms that convert plant-sourced sugars into target molecules, including pharmaceuticals, biofuels, polymers, flavors, and fragrances.

iGEM Students Engineer Biological Tools for a Better WorldiGEM teams show how non-standard natural and synthetic amino acids can be used in 1) peptide synthesis, and 2) disease monitoring and treatment. Both projects make use of gBlocks® Gene Fragments to speed construct assembly.

Creating a Synthetic Immune System for Optimized Immune Profiling—Rad about this high-throughput method for sequencing and quantification of rearranged antigen receptors on T- and B-cells using gBlocks Gene Fragments to create a “gold standard synthetic immune system.”

Review other DECODED Online newsletter articles on synthetic biology and genome editing applications.

You can also browse our DECODED Online newsletter for additional application reviews, lab tips, and citation summaries to facilitate your research.

Author: Hans Packer, PhD, is a scientific writer at IDT.

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