Page 63 - Cell biology PDC 2024

Figure 29: cloning

How can we enter the recombinant DNA in the bacterial cell?

This is called Cell transformation: it is the uptake of exogenous DNA
by bacteria.

Since the efficiency of natural transformation is very low; therefore,
various artificial transformation methods have been used to enter the
foreign DNA inside the bacterial cell. This is done by exposing the
bacteria to conditions that do not normally occur in nature

1) Calcium chloride under cold conditions is used before being
exposed to a heat pulse (heat shock). Calcium chloride disrupts the cell
membrane allowing the recombinant DNA to enter the host cell.

2) Electroporation scientists in this method shock the bacterial cell with
an electric field of 10-20 kV/cm, which is thought to create holes in the

٦۲