$PCR$ is used for:

$PCR$ is a three-step process based on temperature,which follows the sequence of ........

Given below are two statements.
Statement $I$ - The isolated $DNA$ of donor organism is cleaved by suitable restriction endonuclease to form $DNA$ fragments with cohesive staggered or blunt ends.
Statement $II$ - The foreign $DNA$ or passenger $DNA$ can also be obtained directly from genomic or cDNA library.
In the light of above statements,select the correct option given below:

The process of separation and purification of the expressed protein before marketing is called .........

The process of joining together different $DNA$ fragments is often referred to as

What is required for the expression of a foreign gene?