Question

What does ‘competent’ refer to in competent cells used in transformation experiments?

Answer 1

Hint: Transformation is a process by which DNA of one bacterial cell is taken up by another competent bacteria. The bacterial cells have to be prepared to be ‘competent’ so that they can take up the donor DNA. The cells that have been prepared to take up the DNA are known as competent cells.

Complete answer:
The process of transformation involves four steps. The first step is the preparation of competent cells. Donor DNA cannot be passed through the plasma membrane of the bacterial cells. By treating the bacterial cells in heat shock or through electroporation, pores are formed on the surface of the plasma membrane. These cells now have the capability of taking the donor DNA through the pores. Hence, they can be termed as ‘Competent’.
The next step in the transformation process is transforming the cells. The donor DNA is transformed to the competent bacterium.
The third step in the process of transformation is cell recovery and the final step is cell plating.

Additional information:
Transformation is one of the methods of gene transfer used in genetic engineering. Transformation experiment was first performed by Frederick Griffith in 1928. The type of bacteria used by Griffith in his experiments was Streptococcus pneumoniae. Transformation is of two types, based on how they occur. They are: natural transformation and artificial transformation.

Note:
DNA is hydrophilic in nature. The donor DNA does not have the ability to penetrate the plasma membrane of the bacterial cells. So the bacterial cells that act as recipients are made ‘competent’ by various means. Chemically, Calcium Chloride is used to make the cells ‘competent’.