Which of the following is not required for $PCR$?

The entry of $t-DNA$ into plants is associated with which of the following?

Select the option that represents the correct sequence of steps in $r-DNA$ technology.
$(1)$ Insertion of $r-DNA$ into the host
$(2)$ Isolation of $DNA$
$(3)$ Ligation of $DNA$ fragment into the vector
$(4)$ Culturing the host cells in a medium at a large scale and extraction of the desired product
$(5)$ Isolation of the desired $DNA$ fragment
$(6)$ Fragmentation of $DNA$ by restriction endonucleases

Gel electrophoresis is used for:

Describe the method for the isolation of genetic material,$DNA$.

Discuss briefly how a probe is used in molecular diagnostics.