What is the Difference Between Transformants and Recombinants

The main difference between transformants and recombinants is that transformants are the cells that have undergone a transformation, whereas recombinants are the cells that are transformed with recombinant DNA. Furthermore, transformants may or may not contain recombinant DNA, while recombinants essentially contain recombinant DNA. Besides, transformants are selected through antibiotic resistance, while recombinants are selected through the expression of selectable marker genes. 

Transformants and recombinants are two types of resultant cells at the end of a transformation experiment. 

Key Areas Covered 

1. What are Transformants
     – Definition, Features, Selection
2. What are Recombinants
     – Definition, Features, Selection 
3. What are the Similarities Between Transformants and Recombinants
     – Outline of Common Features
4. What is the Difference Between Transformants and Recombinants
     – Comparison of Key Differences

Key Terms 

Blue-White Screening, DNA Cloning, Non-Recombinants, Recombinants, Selectable Marker, Transformants 

What are Transformants 

Transformants are the cells, especially bacteria, that have undergone a transformation. Generally, transformation is the main step of DNA cloning responsible for the production of a large number of copies of DNA of interest. For the preparation of DNA for the transformation, the gene of interest is inserted into a cloning or expression vector. Here, the restriction enzymes linearise vector DNA and ligase enzyme ligates the compatible ends of the vector. 

Figure 1: Transformation

However, after the ligation, the vector may or may not contain the insert. Basically, the recombinant vector refers to the vector with this insert. Then, these vectors are transformed into host bacteria. Finally, bacteria with transformed DNA has to be selected. For that, these bacteria are grown in a medium with a particular antibiotic. However, the vector DNA contains the resistance gene for the corresponding antibiotic. Therefore, bacteria with transformed DNA can grow in the medium. In contrast, non-transformants are unable to grow in the medium. 

What are Recombinants 

Recombinants are the transformed bacteria with the recombinant plasmids. Generally, although all transformants can grow in the medium with the corresponding antibiotic, all of them are not recombinants. Moreover, there are non-recombinants that do not contain the insert. Therefore, non-recombinants only contain cloning vector. Besides, they can also grow in the selective medium. Also, there should be a method to identify recombinants from non-recombinants.

Figure 2: Recombinants and Non-Recombinants

Generally, blue-white colony selection is the method for screening recombinants. Here, foreign DNA is inserted into the sequence of the beta-galactosidase gene on the plasmid vector. Therefore, this insertion disturbs the expression of the beta-galactosidase gene in recombinants. Hence, they produce white colour colonies in a medium containing the substrate X-gal. However, non-recombinants contain intact beta-galactosidase gene, and hence, the resultant enzyme converts X-gal into a blue colour product. Hence, non-recombinants produce blue colour colonies.  

Similarities Between Transformants and Recombinants 

• Transformants and recombinants are two types of resultant cells of a transformation experiment. 
• They have successfully undergone a transformation. 
• Both contain the transformed cloning vector. 
• Moreover, both types of cells show antibiotic resistance and they grow in the selectable medium. 

Difference Between Transformants and Recombinants 

Definition 

Transformants refer to a cell that has undergone genetic transformation through the uptake of foreign DNA while recombinants refer to a cell that contains a combining genetic material with different origins. Thus, this is the main difference between transformants and recombinants.

Significance 

While transformants are the cells that have undergone a transformation, recombinants are the cells that are transformed with recombinant plasmids.  

Type of Plasmids 

Another difference between transformants and recombinants is that transformants contain either a cloning vector or recombinant vector while recombinants contain recombinant vector. 

Containment of the Gene of Interest 

Transformants may or may not contain the gene of interest of the transformation while recombinants contain the gene of interest of the transformation. 

Method of Selection 

Furthermore, the selection of transformants is through antibiotic resistance, while the selection of recombinants is through the expression of selectable marker genes. 

Conclusion 

Transformants are the cells that have taken up additional DNA. Generally, this additional DNA can be a cloning vector with genes encoded for antibiotic resistance. Therefore, they grow in a medium with the corresponding antibiotic. On the other hand, recombinants are cells that contain recombinant DNA. They perform antibiotic resistance while expressing a foreign gene inside the cell. Hence, recombinants can be selected from the transformants by their ability to express a selectable marker. However, the main difference between transformants and recombinants is the presence of recombinant DNA. 

References:

1. “Foundations of Molecular Cloning – Past, Present and Future.” New England Biolabs, Available Here.

Image Courtesy:

1. “Artificial Bacterial Transformation” By Amunroe13 – Own work (CC BY-SA 3.0) via Commons Wikimedia  
2. “Blue-white test” By Stefan Walkowski – Own work (CC BY-SA 4.0) via Commons Wikimedia