Difference Between Gene Addition and Gene Replacement

The key difference between gene addition and gene replacement is that the gene addition is the insertion of a gene by non-homologous recombination while the gene replacement is the replacement of an endogenous gene by homologous recombination.

Gene therapy is a technique that uses genes to treat genetic diseases.  Therefore, it involves the introduction or delivery of genes into patients’ cell. In other words, gene therapy involves the replacement or addition of genes in place of the defective or disease-causing genes. In this process, selecting the correct gene for the replacement or addition is critical. Therefore, gene therapy is still not 100% successful for human disease therapies. Many genetic diseases cannot be treated with gene therapy. But gene therapy is a promising treatment for few diseases such as muscular dystrophy and cystic fibrosis, etc.

CONTENTS

1. Overview and Key Difference
2. What is Gene Addition
3. What is Gene Replacement
4. Similarities Between Gene Addition and Gene Replacement
5. Side by Side Comparison – Gene Addition vs Gene Replacement in Tabular Form
6. Summary

What is Gene Addition?

Gene addition is one of the most practical approaches in gene therapy. It is the process of inserting or simply adding a gene by non-homologous recombination. The adding gene may be an active copy of a defective innate gene. Gene addition technique requires a vector system. Viral or non-viral based vectors are successfully used for this scenario. Retroviruses are the most successful vectors that tested up to now for gene addition technique due to their adaptive nature for delivering genes into cells.

Moreover, with the comparison to gene replacement, gene addition is more successful. However, there are several advantages as well. One disadvantage is the disordered insertion of genes into the genome. Because of this, the inserted genes may be expressed erroneously or inappropriately.

What is Gene Replacement?

Gene replacement is a technique of replacing an endogenous gene at its original locus in the genome. It involves homologous recombination. Using gene replacement, it is able to delete a gene, remove exons, add a gene and introduce point mutations, etc.

Furthermore, gene replacement can be either permanent or conditional. Therefore, the creation of a vector is essential to this process as the vector should deliver the new gene into the exact location of the genome. Furthermore, the transformation is the basic technique that introduces the new gene into a host. More importantly, gene replacement is an alternative to transplantation of bone marrow or stem cells.

What are the Similarities Between Gene Addition and Gene Replacement?

• Gene addition and gene replacement are two techniques of gene therapy.
• Using both strategies, genes can be introduced to plants, microbes, and animals successfully.

What is the Difference Between Gene Addition and Gene Replacement?

An insertion or addition of a gene by non-homologous recombination is the process of gene addition. On the other hand, a replacement of a defective gene with a correct gene by homologous recombination is the process of gene replacement. Moreover, gene addition is more successful than gene replacement. The below infographic presents the difference between gene addition and gene replacement in a tabuar form.

Summary – Gene Addition vs Gene Replacement

Gene addition and gene replacement are two strategies of gene therapy. In gene addition, a gene is inserted while in gene replacement, a gene is replaced. Both techniques require a vector system to introduce the gene. Moreover, because of these techniques, we can successfully treat and prevent genetic diseases. This is the difference between gene addition and gene replacement.

Reference:

1.Morton, R., and P. J. J. Hooykaas. “Gene Replacement.” SpringerLink, Springer, Dordrecht. Available here 

Image Courtesy:

1.”39151355192″ by The U.S. Food and Drug Administration (U.S. Government Works) via Flickr